CEC CD3100 CD player tray belt, puzzled indeed!

Hope somebody has a good educated guess at what the issue is here because it has baffled me so far.

I bought a CEC CD3100 belt drive cd player as non working item.

Got it and as I suspected it was the belt for the tray door, in this case it was so stretched it was just slipping on the drive capstan. A quick down and dirty fix was to cut it and tie it back together in a knot which actually worked surprisingly well and allowed me to play cds to prove it was worth going further.

Could not find anywhere the exact size of said belt so measuring the one I had  ( before I cut and knotted) and deducting approx. 15% for stretch ( figure most sites seemed to state was normal stretch), I ordered a rubber belt from eBay.

Now when this arrived it actually fit perfectly and the tray flies in and out tout suite and I thought my job was done.

Ha, if life was only that simple!

After putting the top cover back on and fitting back into the system cued up the first cd and... nothing!

It spins the cd, reads the tracks and total time but then will not play at all.

Replacing the new belt with the old knotted one and it reads and plays cds again just fine!

My best guess so far is that maybe the new belt is a little too thick ( it was the thinnest cross section one I could find but it is a fair bit thicker than the original).

Now how or why that stops it playing the actual cd I have no idea.

Which is where I hope somebody much smarter than me comes in..... please.. lol.
I cannot explain and do not have time to investigate.  After reading your post and my cec cd3100 also has the belt problem, I divided to try with few sizes of rubber bands.  I notice that it would not read if rubber band is tight.  I just swapped out for the next larger size until it reads.  See if that would help you.  My player works fine now.
I too am looking for a replacement belt for a CEC 3300.  Audio Union wants $100 for the belt.  No can doozy.  If anyone has any new info on sourcing please let me know.  I have a family member in Japan so I'm trying to find a local dealer in Osaka that can get the belt but motivating my family member to help is proven to be most difficult.