To clarify:
The problem persists even in version 7.0.0.9.
I performed a complete uninstall, including deep cleanup, and reinstalled the app from scratch.
I tried using it with and without a VPN, and with different servers in various countries.
Since some speculate that YouTube tracks the activity of logged-in users, I logged out of YouTube, but that didn’t work either. I even tried a completely different YouTube account, also without success.
It would be great if the developers could resolve this issue.