Philips CDM-9 acting up - need help

I’m having a weird mechanical issue with a Philips CDM-9/65. I’m hoping one of the experts here can help out.

What’s going on ?
When the player sits level it doesn’t read the ToC and shows “err” on the display. The disc keeps spinning indefinitely at what looks like startup speed (around 500 rpm).
When I lift the front panel of the player up about 10 cm (4”) it works perfectly normal, reads the ToC instantly, plays fine with no skipping and accesses tracks very fast.

What I tried so far (with no result) :
Cleaned the lens, including the semi-transparent mirror under the laser.
Cleaned and re-lubricated the swing arm bearing.
Checked that the ribbon cable attached to the laser moves freely without catching anywhere.
Cleaned the disc platter and checked it for any horizontal or vertical run-out.
Checked clearance under the disc platter.
Tested the disc motor independent of the circuitry. It runs super quiet.

I’m at a loss at this point. Any ideas would be greatly appreciated.