The selection tool in Adobe Illustrator

It sounds like you have Windows Ink enabled in the Wacom Tablet Properties (and the equivalent in your Huion monitor).

I've complained about it before in this forum, but it is worth repeating again and again. Windows Ink Workspace absolutely sucks! Perhaps it might be okay in relation to a Microsoft Surface notebook and one of its clunky stylus pens. Windows Ink creates nothing but pure trouble for any other kind of graphics tablet connected to a PC.

I have a Wacom Intuos Pro tablet. In order to have pressure sensitive functions in the Wacom Pen the Windows Ink Workspace has to be enabled in the Wacom Tablet Properties. But whenever Windows Ink is enabled it's like an invisible man takes hold of the steering wheel. No matter what I change in Windows settings or even hacks I try to apply to the Windows Registry the situation is just a mess. Most press and hold functions are 100% disabled. If you want to click and move scroll bar in a window, a slider on a CMYK color menu or even move a web browser window you can't do it. The function is disabled. Windows Ink just blocks it. And then there is that aggravating circle icon thing you'll get from time to time. Supposedly the circle thing is supposed to be for some kind of right click function (even though a Wacom Pen has two buttons on the side of it for right-click and left-click mouse functions). Let's not forget about the handwriting text pop up window that likes to rear its ugly head from time to time. That might be the most stupid feature in Windows Ink. I'm using a computer that has a keyboard with Cherry-MX switches. I can type about 1000 times faster than I can hand-write lettering. But Windows Ink wants me to use my computer as if it is a Samsung Note phone. Windows Ink is horribly designed software and has been that way for several years or more. Obviously the guys who came up with that garbage never bothered to test how it worked with third party graphics tablets.

Also, the folks at Wacom, Huion, etc deserve some flak over this too. They know the situation. They've seen the countless numbers of complaints about Windows Ink. Yet they won't come up with drivers that completely bypass Microsoft's totally awful software.

My own solution: leave Windows Ink disabled in the tablet properties 100% of the time. If I need to do any pressure sensitive drawing work I have an iPad Pro and Apple Pencil. That's a product that delivers exactly what it is supposed to do. The settings are easier to manage and do not create road blocks to functions in the installed apps (such as Illustrator).

WHich system is it?

If Mac OS Sonoma, please check if you have the apps Magnet or Rectangle intalled?

Do you have ProofPoint?