Actually the CDM-0 type motor does seem to have brushes. I plan to do some mechanical work on that player this weekend, turning the motor in both directions with force applied to the spindle, and dissembling any bearings I can get at and lubricating them.
The player played for some days without skipping after I lubricated the motor spindle from above and the radial motor spindle from below but and then suddenly became unlistenable again.
Very interesting thread with a lot to read in... Dutch. Before I feed everything into DeepL – how did it turn out? I see you opened the spindle motor and show pretty much wear on the lower bearing plate. Was that the final reason for the oscillation? Or a broken contact in the connector? Thanks!
After I lubricated the RAFOC spindle and after letting the drive motor turn in each direction with external force applied in order to clean the brushes I stopped working on this player. I had only mixed results (aka problem not resolved, only temporarily better then worse).
Thanks again to the amazing community here for so much input.
I thus can confirm that it is possible to grease the CDM-0 RAFOC spindle without any realignment (hold the bolt on top of the spindle, turntable cage needs to be removed, easy, 4 screws, then remove the central nut on the underside of the drive and pull out the spindle by about 2 cm from above).
After @bram jacobse linked me to his findings of a worn steel bearing plate in a CDM-0 motor (above) I conclude that these motors do wear out. They cannot be repaired, as their housing pieces are crimped together. In this regard the CDM-1 drive is much preferable (motor pulley bearing can be honed or changed, motor can be dissembled and cleaned).
Thanks again to the amazing community here for so much input.
I thus can confirm that it is possible to grease the CDM-0 RAFOC spindle without any realignment (hold the bolt on top of the spindle, turntable cage needs to be removed, easy, 4 screws, then remove the central nut on the underside of the drive and pull out the spindle by about 2 cm from above).
After @bram jacobse linked me to his findings of a worn steel bearing plate in a CDM-0 motor (above) I conclude that these motors do wear out. They cannot be repaired, as their housing pieces are crimped together. In this regard the CDM-1 drive is much preferable (motor pulley bearing can be honed or changed, motor can be dissembled and cleaned).
The motor is the main suspect.
The player has a lot of wear outwardly (lettering gone off), so I think it had a lot of playing hours before I got it. Would be consistent with the motor as the problem source. When I spun it with a drill, it did not turn long on its own after taking away the momentum. maybe a hint to friction on the bearing.
I did not open it though. Won't, as this seems really messy, and the motor will be destroyed if I do it.
So yes, my attempt of a diagnosis will remain inconclusive I am afraid.
The player has a lot of wear outwardly (lettering gone off), so I think it had a lot of playing hours before I got it. Would be consistent with the motor as the problem source. When I spun it with a drill, it did not turn long on its own after taking away the momentum. maybe a hint to friction on the bearing.
I did not open it though. Won't, as this seems really messy, and the motor will be destroyed if I do it.
So yes, my attempt of a diagnosis will remain inconclusive I am afraid.
I know you've exhausted pretty much everything else 
Is this a DC motor in this one, I know Philips used all sorts (DC, brushless, Hall effect etc) in the same units sometimes.
Years ago in the early days of VCR's (the old mechanical piano key machines) the head drum was belt driven off a small DC motor and servo problems became common. The cause was the motor and a pretty definitive test was to look at the ripple voltage on a scope across the motor (beware scope lead grounding if you try this). A good motor had less than a couple of hundred millivolts ripple as I recall.
No idea how that would work on these as the motors are smaller. You could maybe see if the ripple alters as it gets close to a skip.
Is this a DC motor in this one, I know Philips used all sorts (DC, brushless, Hall effect etc) in the same units sometimes.
Years ago in the early days of VCR's (the old mechanical piano key machines) the head drum was belt driven off a small DC motor and servo problems became common. The cause was the motor and a pretty definitive test was to look at the ripple voltage on a scope across the motor (beware scope lead grounding if you try this). A good motor had less than a couple of hundred millivolts ripple as I recall.
No idea how that would work on these as the motors are smaller. You could maybe see if the ripple alters as it gets close to a skip.
dear @Mooly , you are tempting me to look into this one... I actually will. I have not yet screwed the lid on I would probably go on looking systematically if it was not that time consuming and I just can't afford to lose so much time with so meagre the hope for a good result.
I also don't feel like spending 150+ euros on another machine in order to swap pieces. I still have a working, untouched 104 with a CDM-1 and some other nice players with TDA1540 and 1541, so I will be able to stay close to my beloved old R2R dac sound. Although I'd have preferred a different outcome.
The Hall motor is in the CDM-1. Philips call the type that normally comes with the CDM-0 "ironless bell-type armature motor". I'd try to transplant the motor if I'd had a donor at hand, but I haven't, and then it is not economically viable.
I would probably go on looking systematically if it was not that time consuming and I just can't afford to lose so much time with so meagre the hope for a good result. I also don't feel like spending 150+ euros on another machine in order to swap pieces. I still have a working, untouched 104 with a CDM-1 and some other nice players with TDA1540 and 1541, so I will be able to stay close to my beloved old R2R dac sound. Although I'd have preferred a different outcome.
The Hall motor is in the CDM-1. Philips call the type that normally comes with the CDM-0 "ironless bell-type armature motor". I'd try to transplant the motor if I'd had a donor at hand, but I haven't, and then it is not economically viable.
So NO scope grounding in this case? As you know I am still a scope greenhorn.
I'll check this just for completeness sake. But even if the result will make the motor less suspect, I've somehow exhausted pretty much everything else.
Nothing lost if its easy to do.
Decades ago we used to sell a lot of the Philips CD150 type players and the RAFOC in those came as a kit with a new servo board as I recall but the manual listed something like three or four possible motor combinations you could encounter. Its all a very long time ago now.
The ripple test could be a good one to try and was very accurate in the VCR's
Ideally you connect the scope across the motor but that is only possible if one end of the motor is ground referenced to zero volts. If not you will have to look at the best way to connect the scope... which end of the motor is driven etc.
Decades ago we used to sell a lot of the Philips CD150 type players and the RAFOC in those came as a kit with a new servo board as I recall but the manual listed something like three or four possible motor combinations you could encounter. Its all a very long time ago now.
The ripple test could be a good one to try and was very accurate in the VCR's
Ideally you connect the scope across the motor but that is only possible if one end of the motor is ground referenced to zero volts. If not you will have to look at the best way to connect the scope... which end of the motor is driven etc.
