This error occurs during check user path for a ".js" GET request and also for one of the GET request from ".googlevideo.com:443/videoplayback". PFA screen shots for error details.
Please let us know how to handle these kind of requests or how to resolve this error?
That Pipelined error is related to HTTP/2. It will be fixed in NeoLoad 6.3.0 that will be out soon.
You can disable HTTP/2 in the Advanced settings of the check virtual panel. If it works you will need to also disabled it in your population settings too.