Subtitles not working unless rename of both video and srt

Hi everyone,

I have a QNAP TS-112 with the latest firmware (3.7.1), so I'm assuming I have TwonkyMedia server 6.0.39.
I noticed that if I have a file with a lot of dots/dashes in its filename (and of course the srt file with subtitles has the same name), the subtitles are not picked up by my Samsung TV. If I change the filename of both files to something shorter, it works. I think it has nothing to do with the TV but only with TwonkyMedia, because the same scenario gives correct results on other media servers (TvMobili, Serviio).
I also tried on my computer with VLC and XBMC, but neither as worked.
I don't know if it's related to the length or to the presence of dots or dashes... sometimes long files with dots and dashes work also with Twonky, but 9 files out of 10 won't work unless I rename them.

For example,

MyFile.S01E01.720p.HDTV-H264.mkv
MyFile.S01E01.720p.HDTV-H264.srt

won't work.

MyFileS01E01.mkv
MyFileS01E01.srt

will do.

If I remember correctly, it used to work with previous versions of Twonky (maybe 6.0.34? cannot remember..)

Do you have any solution to this, or any idea why it's acting this way?

Thank you.