Last year's "orange ring" motor has a 19 tooth pinion, this year's "orange ring" motor has a 13 tooth pinion. This year's gearbox has orange gears and output sleeve, I don't' know what last year's look like?
Make sure you have the right parts, but then it could also be that they don't work together
We're using old FP gears that we took out of the gearbox, with both this year's and last year's motors, to make simple custom single stage reduction gearboxes.