Peculiarity in Marantz PM17 schematics

I've recently got hold of the service manual for Marantz PM17 integrated amp. When studing the schematics I noticed two peculiarities.

First they have double (series) diodes in many rectifier bridge circuits. Why do they do that? I tought long about it and can't find any reasonable answer that makes sense.

The other is that they use many series resistors in some places you would usually put one. For exemple in feedback voltage divider they have three series resistors in a place of the usual one ???

If anyone can shed a light to this, please do so.
 
Ergo, I have seen series resistors used for the following reasons; to achieve resistance values that aren't in the E12 series, instead of one high power resistor, to handle high voltages, and instead of PCB track jumpers, all to save costs. In feedback loops I have seen them used to reduce the temperature coefficient's effect, (according to the designer). I'm sure there are other reasons.

Series diodes, (called stack diodes when here are a lot of them in one case) are usually used to raise the reverse voltage, probably not the case here. I heard they have been used at times to reduce switching spikes but have never tested the theory. Are they series or back to back?

I'm sorry I can't help more, hopefully someone else can.

Regards WALKER