uBO can break sites, but in my experience doesn't to the degree that you're describing. Perhaps you should clear all settings and re-install the extension once and see if that helps?
Do you maybe have other content blocking extensions running at the same time as uBO that are causing 'clashes'?
For me uBO breaks 3D-secure, so it does in fact break every e-commerce checkout that uses it. I just disable the entire extension before I buy something, but it’s rather awkward.
That “enter just your web password here” thing? Don’t seem to for me. Amazon checkout seems to be breaking from something recently but likely not uBO filters.
I'll probably give this a shot. The only settings changes I can remember are allowing things, but I could be wrong. No other content-blocker extensions, I believe.
Do you maybe have other content blocking extensions running at the same time as uBO that are causing 'clashes'?