New data: The problem starts with 2.23.8, incidentally the same release that contain's Werner's modifications to bass figure glyph sizes.I would very strongly suspect 2.23.10 with https://gitlab.com/lilypond/lilypond/-/merge_requests/1409
I'm sorry, stupid mistake: Make that 2.23.10. (I'm juggling things a bit at the moment...)
Lukas