Just to provide some closure to my ramblings about compatibility issues between Qukeys and OneShot: I’ve resolved things to the point I can happily say - no more problems!
I’d hitherto only ever used the command line when compiling the firmware, and indeed when using the Arduino IDE instead (and so not using repositories that incorporate the new plugin hook system), the non-working macros worked again. Other behaviour, which was never consistent, like repeated keystrokes and OneShot keys not ‘shooting’ (when they really should have) also resolved themselves.
A OneShot modifier on a Qukey was also becoming ‘sticky’ a lot too even when I’d set the double_tap_sticky property to false - but this was due to my having set the Qukey property of setReleaseDelay to something > 0. Even so, I suppose the modifier still shouldn’t be locking, but in any case, I didn’t need to mess with setReleaseDelay in the first place as my typing style doesn’t really warrant it.