The following nodes have reported the epicsMutex thread error:

epicsMutex pthread_mutex_unlock failed: error Invalid argument
epicsMutexOsdUnlockThread _main_ (0x2999f20) can't proceed, suspending.

node and log file:

ISI_ITMX_ST2/@4000000054e3b1f036d0862c.u
IMC_LOCK/@4000000054efab210f2ebddc.s
SUS_PRM/@4000000054eceebe32bce24c.u
SUS_ETMY/@4000000054eceebe20a258e4.u

Still unclear why this is happening.  It happened most recently on IMC_LOCK yesterday, and the first known incident was with ISI_ITMX_ST2 on February 16, while I was testing the new guardian release before the upgrade.