The login process get stuck few times for few seconds. I take up to 10 seconds to load a username field, and then up to 10 seconds to load a password page. You can easily try it yourself by going to https://login.ingbank.pl/mojeing/app/#login and waiting for a login text field to show.
It happens on my Windows 11 PC and Ubuntu 20.04 laptop. I have shield and uBlock Origing disabled for the site. It does not happen on Firefox or Chrome.
I have followed your guide, but it did not help. With those settings, I did some testing:
No extra logs in console in Brave compared to Chrome.
Network tab does not show anything loading too long in Brave, but there is clearly a gap visible in waterfall in Brave and not in Chrome. This means that Brave is getting unresponsive for this period, and I can also confirm it by click right-clicking the page: nothing happens in Brave.
Does adding ||ingbank.pl/mojeing/bs/xx.js and/or adding ||ingbank.pl/mojeing/app/assets/js/vendor/bb/$script into brave://adblock help? (guessing here). Does it cause any issues also.
WOW! Adding ||ingbank.pl/mojeing/bs/xx.js actually helped. What does it mean?
Is this a problem with a source code of the website? Why does it OK work on other browsers?