Got another crash from the same file which is 97mb big in tcw2016, so I started tcw2017 and loaded the offending tcw2016 file in and made no changes, then saved as as backward compatible 2016 version.
Closed tcw2017 and restarted tcw2016 and opened the previously saved file made a slight change, then saved and closed the file then noticed the lockfile with extension dwl was still visible in explorer, then minimized explorer the maximized and the lockfile was gone as expected. Closed tcw2016 and no crash.
Repeated the above with tcw2016 without minimizing explorer and tcw2016 crashes, this is weird.
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.