"Push the button and the light dims"...
Your problem is electrical. It's not getting any, or enough, power.
"Push the button and the light dims" tells me that either the toilet isn't on its own dedicated circuit as it should be, shared with nothing else that can pull power away from it or the battery that powers it can't handle the load. Over time, low voltage will destroy a motor.
So first thing to do is check the voltage to the toilet...if it's getting less than a full 12v WHILE FLUSHING, that's your problem. The immediate cause may be a loose connection, corroded connection, weak battery...but unless you rewire it to put it on its own dedicated circuit, you're gonna cook the motor if you haven't already.
If you decide to replace the toilet, I'd go with a Raritan SeaE
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Raritan Sea Era It's designed to be an identical upgrade/replacement for the Jabsco 37xxx series toilets, so even the mounting bolt patterns are the same...and if you go with the 'conversion," you can save some money by re-using your bowl, seat and lid.