I do not doubt you for a second, However, there are others who have raised this issue. I am not the only one. For example:
Can't find my opened tabs, etc.
Below is a screenshot of 17 tabs open.
Next I opened 15 more tabs, but as you can see from the screenshot below only 6 of the new tabs are visible
And as I noted above, I have tried disabling all extensions, but that did not fix the issue.
Can you see all of the tabs you opened?
Using Brave
Version 1.21.77 Chromium: 89.0.4389.90 (Official Build) (64-bit)