Check now Mutex timeout

I have multiple sensors with a mutex that runs a custom exe that may take 10 seconds to execute. The timeout set to 20 seconds. I often get an error result with message "Timeout caused by wait for mutex (code: PE035)" This error frequently is presented when I "Check Now". What would cause this error? My understanding is that sensors that share a mutex are executed sequentially. Is there a limit as to how long a sensor will wait on a mutex for other sensors to execute? When one does a check now on a sensor with a mutex, does it attempt to execute immediately, or wait for the mutex? It would seem appropriate to queue the sensor to execute as soon as the mutex is next available.

mutex pe035 prtg timeout