Question about moving from chain drive to belt drive

Hi all,

I've got a Liftmaster 1/2HP chain drive opener, about 20 years old. It's installed with a one piece rail. P/N 41AC050-2.

My door and opening is 93" high so I'm assuming an 8' door.

The door opener is doing this thing where 95% of the time it works fine and opens the door normally to the top, but 5% of the time, unpredictably and not repeatable, when it raises and gets to the top, the door slipsdown maybe 5" until it then raises again, then slowly drops down, then back up, etc. It'll do this 3-8 times before finally it holds fully open. Not sure if it's a brake issue or what. Anyway first question is, if anyone has feedback on how to address this issue I'd take it and maybe fix it.

https://www.youtube.com/shorts/HWDZEFS4oT8

Anyway as an alternative I'd like to consider a Belt Driven unit. Locally here the Chamberlain B4505TC is on sale and looks suitable.

The second question I have for this group, is, say I buy the B4505TC, spend the extra money to buy the 8' door kit to get the longer belt, would I be able to keep and use my single piece rail? Or would I have to use the multiple part rail in the new 8' kit? I'm unsure of the compatibility of these rails...

Thanks!