I made a slight modification to test/format to expand the length of the snap list (as suggested in WT-7023) and saw this:

 t: process 28875 running
snapshot-isolation 0000225348.00/opqrstuvwxyzabcdefghijklmnopqrstuv search mismatch
expected {0000225348/L}
   found {deleted}
t: run FAILED

The "found deleted" is equivalent to seeing a WT_NOTFOUND error. I've saved the failing directory, and will attach the CONFIG file and the mods.

This failed on my virtual workstation. I'm running the CONFIG again now, but I haven't seen the failure.