system volume intermittently increases to 100% and is locked to that value for several seconds. (logs included)

MacOS High Sierra

Version 10.13.6

Macbook Pro

Mid-2015 model

This has been happening once a week for a few weeks now.

I will have my headphones plugged in and listening to a song on youtube in a browser (Chrome) at around 40% system volume. Seemingly randomly, the system volume will jump to 100% and appear to be "stuck" there for several seconds. Using the F11 (volume down) or F10 (mute volume) keys do not working during these several seconds where the sound appears to be stuck to 100%.

I searched the console logs for "audio" and the only logs mentioning the keyword audio actually have a timestamp around the same time the incident occurred.

default 12:09:40.666808 -0700 systemsoundserverd 202: AudioFileReadPackets:result 0

default 12:09:40.667296 -0700 systemsoundserverd 687: -> Incoming Request : actionID 4096, inClientPID 27213(Console), inBehavior 1, customVibeDataProvided 0, loop 0, loopPeriod 0.000000, inFlags 0, inClientCompletionToken 1

default 12:09:40.667724 -0700 systemsoundserverd 203: Data was marked NON-purgeable for actionID: 4096; this: 0x7ffe2da0fc00

default 12:09:40.669963 -0700 kernel + IOAudioEngineUserClient::externalMethod, selector=0x0, arg0 0x0, arg1 0x1079dd000, arg2 0x8010 arg3 0x65

default 12:09:40.669980 -0700 kernel scalarInputCount=0x4 structureInputSize 0x0, scalarOutputCount 0x0, structureOutputSize 0x0

default 12:09:40.669451 -0700 systemsoundserverd 992: -> Starting audio : actionID 4096, volume 1.000000 (user vol 1.000000, client vol scalar 1.000000, CM vol 1.000000), pan 0.000000

It seems that the "systemsoundserverd" process began "Starting audio" at a value of 1.0 randomly out of nowhere?

Longer snippet of logs attached

Many thanks!