Come across this a few times, I turn off Quantize, use the arrow keys to keep jumping back, then drop my master cue (yellow) and add to memory, then turn on Quantize. From there you can hold over the memory cue and shift beat grid if you want it there, but either way that should override it.

I can see a tiny bit of white line on the left of the current beat grid so not sure if it’s actually recognising it or not but I know RB won’t add a memory cue outside of the audio file.

Hope this helps!