Have you tried downloading your file and chamfering it. yes I know you will have tested it before posting, but I tried your file and it chamfered ok, all side one at a time. (using v2018 pro on windows 10. ## Edit ## Sorry I had not understood the problem correctly, I only realised after Henry's post. ## End Edit ##
Maybe Henry will have more luck at reproducing the problem. The difference between doing all at once and one at a time, is how it creates the three way corners.
With regards the offset. when one of the offsets are 0 (zero) it defaults to 45 degrees because one cannot offset zero. I tried setting offset 2 to 0.2 and 0.6, both worked fine.
Regarding the mouse, there is a setting in Tools menu - Customise - Options tab - Additional device setup. you could check in v21 and v2018 and set them the same, whether it will make any difference I've no idea, when I tried altering the settings and assigning new things, I didn't take any notice, probably being overridden by my mouse software. but then again I've always used the mouse wheel for just zooming.