It would be great if there was a function within the OpenComputers support to reset the player arm to default (thus allowing tracks to be started and reset by computers).

I imagine just a .resetPosition() function would be good enough.

Doesn't .stop() do that?

I can't see .stop() in the component list (using =component.record_player to list all of the function, .stop() doesn't appear in that list.

But yes, it does work.

I think this is an OpenComputers display issue, not a problem with your mod. Thanks for your help :)

The built-in Lua interpreter doesn't show whole tables, just parts of them unless they're very small. So no, that command won't list all of the functions.