This can for example manifest as:
Assertion 'CellBlock < RegistryHive->Storage[CellType].Length' failed at ../../lib/cmlib/hivecell.c line 32
Assertion 'KeyCell->Signature == CM_KEY_NODE_SIGNATURE' failed at ../../lib/cmlib/cminit.c line 115
Happens on testbot all the time now.
A note from reactosfanboy:
Read https://reactos.org/wiki/Registry and especially http://amnesia.gtisc.gatech.edu/~moyix/suzibandit.ltd.uk/MSc/Registry%20Structure%20-%20Main%20V4.pdf (grep for ".log" to read how Windows does registry writes in transactional way)