Classic Starter motor query

Usual starter motor problems meant I had to change the current starter motor, didn’t have time to order a new one and as this was a bit of a rush job used one from a competition motor I’m building.
Fitted a power lite high torque starter, anyway it spins up fine and catches almost immediately but after it catches there’s a sort of gear grinding / over compression sort of noise. Anyone had any issues with these starters

yep they can be troublesome, a quick razzle with a mallet