First, almost all the automatic film counters will jam up with dirt and old lubrication, so will need a CLA to function correctly.
There are two types of counters that I know of.
The most common are the ones that count turns of the take up spool. These often have a problem with modern thin base films, but often work OK with thick based films like Fomapan.
The second type meters the film by picking the emulsion outside the frame with a star wheel. My Iskra has this type of counter and gives very even 1/8" spacing along the entire length of the roll.
Many of the Iskras were converted to red window. Probably not because of lack of parts as often attributed, but more likely to get 16 exposures, and save on the cost of film as the Soviet economy deteriorated. With the removed parts lost or misplaced it became difficult to convert them back.
In my little collection I have a Yashicamat TLR, the Iskra, a Hapo, and a Kodak Monitor mechanical film counters. The only one that meters the film precisely is the Iskra. All the others have rather uneven frame spacing.
One of the things you can try with your red window camera is different film brands, some have numbers that are easier to see than others.