Unparseable microdescriptor on public relay

A relay operator reported this error:

Get this at my exit relay since yesterday:

# head /tmp/warn.log
Oct 23 23:30:17.000 [notice] Tor 0.3.5.3-alpha opening new log file.
Oct 23 23:30:33.000 [warn] parse error: internal NUL character.
Oct 23 23:30:33.000 [warn] Unparseable microdescriptor
Oct 23 23:30:33.000 [warn] parse error: internal NUL character.
Oct 23 23:30:33.000 [warn] Unparseable microdescriptor

even with log level "debug" there seems to be no more information.
Anything I should worry about?

https://lists.torproject.org/pipermail/tor-relays/2018-October/date.html