Hi !
It is good to know following:

Cqrlog can be compiled for GTK2 widgets or QT5 widgets. The program is same but graphical layout has some differences. Recently I found out that QT5 file open dialog has a major difference with GTK2 one (that I have not used for long).
With QT5 file open dialog it is possible for user to type in the file path and file name. WIth GTK2 this can not be done and file must be found with browsing using the dialog's file browser.
Cqrlog uses file open dialog in several places. Common for them is that file path and name that dialog gives is not checked to be valid.
Using QT5 file open dialog by typing wrong file path and/or file name it happens that file is not found and Cqrlog is not prepared for that.

It will cause different kind of error splashes with "Abort" or "OK" buttons.

Most of them are harmless, but there is on that must be warned: "Qso_list/File/Import/DXCC data"
That is used if you want to import a new DXCC county file manually.
If it happens that you type wrong filename here, and the file is not found, Cqrlog will wipe out database "cqrlog_common" table "dxcc_ref".
And if that database table is empty you can not start Cqrlog any more. it will give " ** is not valid integer" for every log you try to open.
And if you cannot open Cqrlog you can not import new dxcc_data.

Then becomes a question of backups. If you have "save log data to local machine" in use and you have copied ~/.config/cqrlog folder for safe place returning ~/.config/cqrlog/database folder contents from backup can make Cqrlog start again. But you may loose some qsos depending on how old your backup is.

If you use external database server and have dumped all cqrl% named databases you need to return cqrlog_common database dump. in this case your qsos are not lost, you are just getting old dxcc, iota and qsl manager lists. Perhaps also some log(s) may be missing from startup list if you have created them after last backup. Also in this case those logs still have their qsos in database and it needs a bit more work to get them visible again.

So it is good to have fresh backups in every case.

You have been warned. Nothing happens (at least for this reason) if you use QT5 open dialog's file browser to find your file instead of writing the path and filename directly.

This will be fixed in Alpha version (114 and up) of Cqrlog.
For official version I can not give any guarantee as there are so much pending pull requests that I have stopped for making new ones and Alpha version has therefore gone so far ahead that new fixes for it do not fit any more to official source without extra work.