Error condition spotted on v8.1.4 LTS - mutexLock nested! file.c:216. mutex:127 in _health.qo

Troubleshooting
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1

Hello,

In the process of upgrading our fleet of devices to v6.2.5 LTS and/or v8.1.4 LTS.

We caught a device on v8.1.4 checking in to Notehub with _health.qo looking like:

{"text":"boot (*** mutexLock nested! file.c:216. mutex:127 [17149] [3.0] G:Gp:W~ M:Mp:W900 U:W0 R:Rp:W0 S:Sps:NS:FSwnopen:TLOGab1 T I:W~)","voltage":3.9765625}

What is this?

Thanks!