This is a previously existing latent bug that has been exposed by SERVER-80563, where sbe::UnwindStage does not correctly handle child yields and thus references memory (in UnwindStage::_inArrayAccessor) owned by a WiredTiger cursor that has been freed after a child yield event.

Apparently the prior internal uses of sbe::UnwindStage (e.g. in the SBE $lookup implementation) did not have the possibility of a child yielding under this stage, so the yield code paths were not exercised before. It looks like the bug has been latent for ~3 years.