Here are more suggestions:
1. May I assume that you have deselected Vivaldi in its preferences?
2. Use Disk Utility to run Repair Disk. You don't have to boot from the Recovery partition to do this. However, the computer will be locked up while it's running.
3. If you don't want to do the above, you could start up in
Safe Mode That automatically runs Repair Disk (which is why it's so slow). If the problem does not occur in Safe Mode, that may tell you something.
4. Download and install the
10.15.2 Combo Update That won't hurt anything and has cured strange problems for me in the past.