Hello ondrejz, I got a report of the same issue in the Japanese forum.
I can confirm the issue on my machine, too.
Repair nor reinstall does not solve this issue.
1. Launch SafeZone Browser
2. Open some pages
3. Click "Card" icon to switch Bank Mode
4. Bank-mode screen appears, no SafeZone Browser opens
5. Back to normal mode (Bank-mode is running), SZB is unresponsive now
6. Switch to Bank-mode, SZB is there but unresponsive
* Only browser (and Bank-mode itself sometimes) freezes
* DO NOT try to close SZB from inside of Bank-mode, or Bank-mode will be unresponsive too and getting out of Bank-mode becomes difficult
* Unable to kill SZB, saying "Access denied"
Windows 7, Avast Pro 17.2.2287