I just bought a used Riso HC 5500. Mainly for printing envelopes.
Machine seems to be in GREAT shape.
However, I am getting a "random" issue that is occurring when printing envelopes.
The printed envelopes will pick up random "stains" of ink. All color, and in different places each time.
If I just run "flat" 8.5 x 11 paper through the machine, it seems fine.
It seems that the "thickness" of the paper or the envelopes is what is causing the problem to appear.
See attached photos for samples of the problem.
Thanks in advance for any help or tips on solving this.