Proto GP18 "loose" motor/mount

[Upstate Gator]

I have a split frame Walthers GP18 that I'm installing a Digitrax Dn163k2 in. Besides the fussiness of the slightly too short motor contact on the bottom, I'm having issues with the motor sitting loosely enough in the frame that the motor mount(?) is rocking slightly side to side as the motor engages, leading to contact issues and rough running. I have another GP18 that does not have this problem. Any suggestions on why the motor mount could be loose or how to remedy this issue?
Thanks,
Ben

[Upstate Gator]

So, is a motor mount that rocks up and down not a problem, or is there something obvious I'm missing?

[Upstate Gator]

Problem solved  Used a bit more Kapton tape, and the motor is secured.

[Carolina Northern]

I haven't put decoders in my 18's yet. I'll keep your solution in mind.

Thanks,

Don

[Upstate Gator]

@Carolina Northern The contact through the brass tabs is so-so on both sides of the loco and I may still need to hardwire the the other side as well. (I may have exacerbated the issue with removing the decoder multiple times, plus using a previously-installed decoder from a Kato RS2.)

Ben