Photoshop: Straight Brush Lines broken in 21.1

Windows 10 PC.  It does not look like WinTab is running if I look at the list of drivers in Command Prompt.  I've also had Windows Ink turned on and off in the Wacom preferences and it gives me the same problem either way.  This does this both with the Wacom table, and with the mouse, and still does it if I unplug my tablet and reboot with just the mouse.

Jeffrey, I have made a test now with WinTab and WinInk, and this problem is related to WinTab. There are other problems which have also occurred with WinTab in the latest release (like end of stroke cursor draws a instant line to the left edge of the screen some times). So currently in 21.1 WinTab is nearly unusable.

PS! The ideal solution would be to actually fix WinInk implementation in Photoshop properly once and for all, so nobody need to use WinTab (since WinInk is a more optimized driver). But currently, there are several annoying issues which makes it bad for artists (though it has improved lately) First thing is that one has to put all the WinInk Windows settings correctly for it not to be horrible - those things should just be disabled in Photoshop (like all the cursor effects, press and hold, etc...)
But there are problems that are impossible to fix. Such as: There's always a few milliseconds lag for the first movement you do after a small break or if you go from painting on a canvas and to a menu item and back or press the pen to long, you will feel a stutter (this doesn't happen with WinTab). Also the annoying "shift" "ctrl" and "alt" bubbles that pops up under your cursors when you press the keys.

I think if the issues in WinInk/Photoshop were fixed it would be the best solution for everyone and nobody needed to force Photoshop to use WinTab - And I think it's something Adobe should prioritize to fix, since a lot of people use Photoshop with a tablet. I would gladly be on a test panel if Adobe could prioritize this. It's been a problem ever since WinInk was introduced to Windows and you see hundreds of discussion forums of users that needs to figure out how they can get photoshop to work properly with a tablet. 

Barry, I suspect you didn't turn off WinTab when switching to WinInk. If you still have the Userprefs.txt document in the Photoshop settings folder with #Use WinTab, you won't be using WinInk, even if you turn it on in Wacom preferences. 

Not sure if this is helpful, but I can't record a video unfortunately.

Sometimes holding shift first does result in a straight line, but it's not a consistent result.

I have the same problem and was going to report it. After 21.1 the shift drag is worse than before. The problem is: Before no matter when you hold shift you could draw straight lines. After 21.1 you have to hold shift before you start painting. if you click shift after you started drawing the stroke it will have no effect. 

It's very difficult to record this, because you cannot see when I start holding shift or not. But I think its a consistent problem of 21.1. 

same thing here, tablet not connected will try to uninstall driver

What worked for me was to remove the UseSystem Stylus config file I had put so Photoshop would use the tablet sensitivity and not windows ink which was not working.