if your directional contactors are pulling in but you are loosing travel i would suspect the directional contactor tips being worn or the armature parts inside it are worn and hanging up causing it to not pull in correctly and loosing connection.
If you have travel and then not it could be the tips are either burned or just worn enough to not make a good connection every time they pull in causing it to loose connection and have loss of travel.
These contactors when they get worn will also hang up and not pull in completely and as they warm up it can get worse which would explain the increased frequency of travel failure as you continue to drive it.
Take a look at the forward/reverse contactor assembly and see if the tips are burned or flattened out.
Another test to try is to jack up the drive wheels off the floor, get the truck to start acting up again and while it is in the no drive state go to the forward/reverse contactor assy and wiggle the tip assys and see if it returns to driving normally.

Alot of what has been described in the previous threads you've posted is sounding alot like the fwd/rev contactor assy is worn out or burned tips in it.

Best remedy to repair this is to just replace the contactor assy, you can try to repair the contactor assy by installing tip kits but the parts, labor and time to do this would cost more than just swapping it out with a new one.

Although these EV100 systems are known to have issues with the recs #2 and #5 and an occasional #1 failure these are usually accompanied with a fault code. Since you do not have any faults showing this is what has led me to this conclusion about the directional contacts.
If they are worn and loosing connection this would explain the loss of travel with no error codes.