I have been using my introus with clip studio and photoshop with no problems.
So a couple of days ago I see that Krita is free and thought I would have a go, but there seems to be a major problem.

I start up Krita and open the screen and start drawing. At first everything is fine, and a few minutes later I lose all pressure sensitivity and I get a horrible thick line.
No matter what settings I try I cannot get pressure sensitivity back once it goes.

However I have found a little trick. If I run photoshop and Krita, and start using Krita.
After a couple of minutes I lose pressure sensitivity, so I switch to the photoshop screen and draw I have correct pressure, then I go back to Krita and it works fine for a few minutes and then I lose sensitivity again. Back to photoshop, draw one line and back to krita and then it is fine again for a couple of minutes.

It is not a driver issue as I have the latest driver for my tablet, and I regularly use photoshop, clip studio, autodesk sketch.

I know Krita is free, but I don't know what is causing this bug.

I'll assume that you're using Windows 10. Are you using krita version 4.2.8 which is the latest stable release?

The Wacom Intuos tablets have a Windows control and setup utility which you should run and look at. You can set up different 'profiles' for different applications and the driver will know which application is active at any particular time. Try to set a profile for krita, when only krita is running. It doesn't need to have any particular characteristics but the fact of there being a separate profile for krita often solves some kinds of problems. The different profiles are shown as application icons along a section of the control/setup utility window, as I remember when I did it with my Wacom Intuos Draw tablet.

Hi ahabgreybeard,

I will give it a go tomorrow. Will let you know.
I am quite impress with Krita apart from this problem.