TTML region/style not applying properly

[obsrvwr]

I'm having issues with making TTML styles or regions work. Even if the region/style appears to have been updated in the list view, no changes are reflected in the video display. Uploading the caption file and viewing it in a different program unfortunately doesn't change anything.

Changing the colors/alignment using the non-TTML formatting options (color, alignment) that are available for other file formats like SRT works. Even VTT positioning works. I'm just not sure what's wrong with TTML specifically.

Looking into the source file shows the style tags being added to the subtitles, but not the region. However, if I change the alignment by inserting {\an1} into the line, a region tag gets added into the source file and shows in the list view upon reloading.

I have also attempted to change the default style but to no avail.

(I don't think I can upload TTML files to Github? So I've pasted it into a TXT file)

ttml-formatting-test.txt