Notes disappear with Fundamental ADSR in poly mode when channels > 4

[cschol]

Hey guys, I found that Fundamental ADSR misbehaves (some notes just disappear while playing) in poly mode when channels > 4 and I stumbled upon this issue, I feel it's related.

How to reproduce: start connecting a positive gate sequentially from any channel <= 4, one by one, while looking at 5th, 9th, 13th output chans of the ADSR.

How to fix temporarily: always max out channels up to 16. But the catch is this will max out cpu usage as well, because 16 chans will propagate to the rest of the patch.

I'm on win10, Rack 1.1.6.

Originally posted by @ptytb in https://github.com/VCVRack/Rack/issues/1393#issuecomment-695752943