Fairly inexperienced user here. I have made several videos with SRT files for the captions. No problems until the latest attempt. The MP4 is fine but the SRT file has a weird extension and is empty everytime I export it. The SRT name is as shown here: Name.mp4.26460.18560.SRT
I just tested in PR 22.3.1, and it still works the same. I deleted the third of four captions (so it says "<Type your caption here>). When I export srt from "Sequence 01" (from the Text Panel, Captions Tab, 3 dots, but any method works the same), I get a file name "Sequence 01.12836.5212.srt," which contains only the first 2 captions.
For better or worse, PR does not allow exporting empty captions and does not warn you that it is truncating the export file.