Sudden performance drop in 2021

Hi,

I am a brand new user of Corel Painter 2021, although I did use the product some ten or twelve years ago on a client project so I have a little familiarity, albeit outdated (I am an experienced graphic/media software user in general). I am running Painter on a <6 month old Windows 10 pc, i910900X CPU @3.70GHz, two Nvidia RTX2070 Super GPUs with NVLink, 64GB RAM and fast P2 storage. I have to really try hard to get bad performance out of this machine, even with heavyweight 3d modelling and video editing software (I run a modest media production business).

When I installed Painter yesterday I ran the optimiser and got a score of around 9750, described as 'awesome' and suggesting I would have no issues with brush performance. And indeed I didn't. Everything was super slick and I didn't experience a single instance of lag with any brushes I used. I tinkered for three or more hours without a hitch,

Today, however, it's a very different story. Although I still get the same score when I run the optimiser, no matter what brushes I use, performance is dire, with lags of several seconds after most brush strokes before I can use the brush again. I have also had three crashes to desktop.

I am not aware of any Windows update overnight that might have caused this and the only thing that I have knowingly added to the installation was the free brush pack available on the store.

I have started Painter while holding shift in order to start with a vanilla version but it has had no effect on performance.

Rather than blindly try lots of other potential remedies, may I please ask the group if there is any prior knowledge of this kind of thing and whether there are any prescribed steps I can take to either diagnose the root problem or, ideally, cure it.

Thanks for any help.