8 piece classical guitar orchestra with electric bass. No headphones, so a bass amp was set as low as possible in the room, which was the way the piece was played on a tour. There are a LOT of ways an electric bass can sound, from clean to aggressive, and there was no particular note about it. Some sections of the piece are fairly aggressive.

Problem - the composer/producer did not attend, and was bothered by the sound of a bass string buzz that sounded somewhat like a snare rattle in the full mix in one sparse section that starts with bass followed by guitars creeping in, some playing just harmonics. None of the other 12 people in attendance noticed it or were bothered by it while getting sounds and auditioning takes.

8 individual guitar mics
Bass DI and mic on amp
Ambisonic mic in the center of the guitar semicircle, same plane as the 8 individual mics.
AB omni overhead pair
Blumlein ribbon overhead pair

The bass sources lacked the sound, the overhead pairs lacked the sound, and it could be found in the ambisonic if set to a maximizing position. The ambisonic (at least as I was using it) was set to point up at the ceiling for maximum room ambience, minimum direct sound. No rattle in it.

The 8 guitar mics have a lot of the offending sound. Same horizontal plane as the bassist who was behind the semicircle, so guitar mics secondarily pointing somewhat in the direction of the bass. It was the acoustic sound of round wound strings slapping the neck and frets while played aggressively. The amp was behind the conductor facing the guitarists, as a side note.

I suppose if I'd put a mic on the bass as if it was another acoustic instrument it would allow a shot at using something like RX11 to remove the slap from the guitar mics. That's a first for me, as a thought. That theoretical preemptive fix makes sense - in retrospect! The amp or DI signal is only really useful for reducing the low end bloom in the room. A small gobo blocking the acoustic bass slap from the room would have been useful too; alas there was not one available and no sense that one was needed.

Anyway......FWIW as a one-off story, a situation I'll probably never encounter again.