Hi,
Sorry to revive an old thread… I’ve found an issue importing SRT subtitles with tsMuxeR, and maybe this info could be useful to someone (assuming the problem is not due to my fault or related to my PC configuration):

I’ve used tsMuxeR 2.6.11 (on Windows 10) to convert SW and ESB Despecialized Editions in blu-ray disc format, including some of the available subtitles by directly loading .srt files in tsMuxeR.

When playing the disc I noticed that the last text item of every subtitle track was not shown (for example, the text “…ha inviato migliaia di sonde fino ai più lontani confini dello spazio…” in ESB-it-titles.srt, or the text “Ow!” in ESB-en-16mm-mono-native.srt).

I resolved the issue by adding another newline at the end of every .srt file.