Thanks @gsp_runner but I have tried all of the obvious workarounds and settings to no avail ... so far none of these changes have made any difference to the fact that the rewind key is not repeating.
Am I correct to think that repeating, constant rewind would be the expected function ? (This would distinguish it from “Step back”)
I have tried resetting the hot keys to the defaults on the function keys, and to other random keys. In this case, neither the rewind or fast forward buttons are repeating. I still have a copy of ExpressScribe 2 (version 7.01) on an old MacBook (OS X Sierra) and the reverse button is still repeating there. On the same old MacBook, reverse is not working in ExpressScribe 3 (version 8.13). I have tried matching the settings from Scribe 2 on the new Scribe 3 but this has not fixed the problem. Unfortunately, Scribe 2 does not run on the new MacBook M1 2021 with OS X Monterey.