DOSBox SVN Daum isn't supported here.

With that said it's possible DOSBox SVN Daum is using a newer version of SDL that is incompatible with Windows 10 Fall Update. Try copying the SDL.DLL from DOSBox 0.74 which uses SDL 1.2.12 into the DOSBox SVN Daum directory.

SDL mouse code was changed in SDL 1.2.14 which is incompatible with Windows 10 Fall Update but supposedly this will be fixed in a Windows update eventually.

So thats the reason my mouse goes screwy in SVN Daum!? I did notice my mouse works fine in standard DOSbox .74 but like the OP posted mine does the same thing in SVN Daum. I hadn't been using it that much lately because now that I have an actual MT-32 module and my MT-200, I didn't need the built in mt-32 emulation.

Also my mouse is crazy in SVM Daum regardless of which video mode I choose. I tend to stick with Overlay I believe with no filtering. That way I get the right 4:3 aspect at full screen on my display with wonderful blocky pixels and all.

I will give this a try myself later and see if it solves the issue on my setup.

Daum is broken and has been for some time. Its developer no longer supports it. It is time to move on.

I would agree, but the issue is that Daum seems to handle video mode switching FAR better than the standard release of DOSbox .74 does. Not sure why as I have the same config files for each minus the extra stuff that Daum adds in. But the screen scaling doesn't match between them with Daum's looking far better on 4:3 through a 16:9 vs the .74 itself does and when I exit a program on standard .74 there is always a second or two of massive glitched graphics before I get my command prompt again. Daum doesn't do this so it would seem that Daum and whatever else it has for video is far more compatible with my GTX 1070 than standard DOSbox .74 is.