Error: Cannot kill process or thread with moniker "1". The specified process or thread was not found

I observe this error:

"error: cannot kill process or thread with moniker "1". the specified process or thread was not found"...

at the begging of any test run in performance center 12.53 patch 4. The load generator is installed, in standalone modality, on a windows 10 platform. (It isn't a problem of regional settings)

Can anyone help me?