I don't know when it changed but I used to be able to drag a subtitle file from my NAS and drop it into celluloid to activate subtitles. Now I have to pause the video and use the menu to open a subtitle file.
In troubleshooting I find that I can drag any file into any compatible program and it will work if the file is dragged from a Home directory or any hard drive on my PC but not if the file is on my NAS. Double clicking on a NAS file works fine (double clicking on a subtitle file is not an option). Using the program menu to access the NAS works fine. Drag and drop does not.
As an example, dragging a PDF file to Chrome works from any Home directory or local hard disk but not any NAS directory.
Never saw this problem before a month or so ago.I needed to upgrade my kernel to 6.2.8-060208-generic a while ago (a month or so? maybe? I forget why I needed to do that). I tried upgrading to 23.04 but I rolled back to a backup when it didn't work for me. So I am now on 22.10 with 6.2.8-060208-generic. NAS is WDMyCloud v04.06.00-111 (obsolete/EOL)
Edit -- I only navigate to my NAS in Nautilus through 'Other Locations' and the user id and password is remembered from the first time I did that. I don't explicitly use fstab. I never have any problem cutting and pasting files to any directory I chose locally or on the NAS. File operations are easy. Dragging a file and dropping it into an application is my problem.
Edit -- I finally upgraded to Ubuntu 23.04 and the problem went away (my previous attempt at 23.04 failed on a sound card problem). I can't remember when I upgraded to 22.10 but it was pretty late. I suspect my problem was confined to Ubuntu 22.10.