Yes, It's an ICS Standard. Nice machine.
This is my guess:
The belt is still too loose, or just worn out.
Oil!
The carriage should slide smoothly along the carriage rod, otherwise it could create drag. Put some oil along the carriage rod and slide it back and forth. It should slide effortlessly with no drag.
I'd also put some oil along the feed screw. The half-nut may need be adjusted. It can't be too tight or too loose when it engages with the feed screw. Remove the feed screw cover and take a look to see if the half-nut is fully engaging with the feed screw properly, and if it is moving along smoothly. (Again - oil.) You can also adjust the rod that holds the half-nut so that is is slightly closer to the feed screw when in the playing position if you need to.
Also, when the carriage is resting against the top of the repeater (the long flat part) it might also create some drag. I've encountered this with ICS machines, if memory serves. Put some oil along the length of the repeater where it might touch the carriage.
Oil the rest of the machine while you are at it, like this:
https://www.youtube.com/watch?v=wYUG5z7nloI
Good luck!