Hi Yuriy,
I used the latest version in my test. The hardware is not the most recent but still good to work with (iMac 27" from 2019 with a 6-core i5 Intel CPU, 16 GB RAM and 500 GB NVMe drive).
The forum post I mentioned is this here: High CPU usage when idle
I abandoned the test of FontBase because of the described issues, uninstalled the software and use Typeface instead: there was no problem at all to import exactly the same former FontExplorerXPro archive with hundreds of subfolders and several thousand fonts within a few moments. All have been recognized and are usable.
Thank you for assistance and best regards