[FrankJ]

Looking at your pictures.

If you are ratcheting, either the CD is changing or the chain is elastically stretching. CD changing seems more likely to me.

You definitely have some drive sprocket wear. Whether or not it is enough to be an issue, hard to say. The wear changes the pressure angle which can increase chain tension for a given torque. Maybe trade the idler sprocket for the drive sprocket?

Make provision to take up slack in the chain?

The motor support & motor sprocket has a lot of cantilever. Run a piece of flat bar to the frame rails or wheel gear boxes to add a bearing to help support the gear box shaft?