DvR 17 Studio - Timeline freeze/crash + render failures

I have looked at other postings on timeline playback problems with DVR 17.0 but have been unable to find any solution to the problems I am experiencing since upgrading from 16.2.8 Studio to 17.0 Studio (I didn't use 17 Beta).
I am editing a 1080p project with .mov files from Canon 7D which gave me no problems in 16.27.
I now have persistent, frequent and seemingly random instances of: 1. Timeline freeze (on clicking) for anything between about 5 - 30 seconds or more. 2. Occasionally leading to complete crash. 3. Regular, seemingly random/ render failure (cannot process video file). 4. Occasional mis-reporting 'Media Offline'.
I have already rolled back latest Nvidia Driver to 460.89 (clean install) and have tried both checking and unchecking the 'Decode H.264/H.265 using hardware acceleration' (Nvidia) option in Preferences / Decode Options. (Surely this should be checked...?!)
Anyway... I am at a complete loss... all advice / assistance gratefully received!

UPDATE:
I have just updated to DvR 17.1 Studio.
Initial impression is that there might be an improvement in Timmeline behaviour.
Some short freezes of up to around 5 seconds max when clicking on a playing timeline, but no complete hang/crash.
Will post again after further testing of Edit timeline editing and Delivery rendering out.