I agree with what the previous post suggested; take it apart, clean everything while comparing to the manual to verify there are no hacks made to the assembly. If any plastic have dents or is broken then replace it.

I also reacted to you writing about rubber, there are no rubber parts in the gumball machine.

There are no rubber parts at all in the gumball assembly; if you have one it's a hack and should be removed.

I agree with the previous poster; disassemble it and clean all parts while looking for dents, broken plastic or anything else that shouldn't be there.

Here are some pics from when I last serviced my assembly for reference.

The motor turns the white wheel above it, which in turn have a plastic prong that moves inside the black cross-shaped plastic and turns it. The black plastic is fixed to the axle that in turn rotate the red plastic with four holes in it, making one ball to drop down below and roll out to the PF.

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Get a replacement housing and get rid of that problem forever.

If you do some half assed repair it will probably keep giving you problems in the future and as its a PITA to access/remove the gumball machine its just not worth it.