CleanupHandler not always running

Hello Mod_perl-ers,

I've got an app that increments a counter in redis in a
PostReadRequestHandler and decrements it in a CleanupHandler.  I'm noticing
a small amount of cases where the counter doesn't get decremented.  There
are no segfaults but there are a small number of "Apache2::Filter internal
flush: (-3) Unknown error 4294967293 at -e line 0" messages.  Looking at
the source code, I believe a modperl_croak is getting called in this case.
Would this cause the CleanupHandler to not run?  What exactly happens when
modperl_croak is called?

Thanks,

Paul