I hate the ice cream machine. (USA)

I have been cleaning the ice cream machine for years. I was even sent to classes for it.

Does anyone else have an issue with the shake side not properly working after changing the little plastic o-rings from the tune up kit?

Every single time I change it, the shake side for whatever reason decides to not dispense shakes.

https://imgur.com/a/ORKIno0

That piece will lift for a split second and then go back down only dispensing syrup.

Everything is assembled properly. It just only happens with new o-rings from the tune up kit. Eventually after fucking around with it, it randomly starts working. But I honestly haven't a clue what causes the problem in the first place other than it only happens when changing o-rings.