[Ghitulescu]

Load a black video in pot, attach these subtitles, set the output to file, then via a script save as bitmap every changed frame - replace the bitmaps of tsmuxer/easysup with the new ones (manual, script), then see if they need to be repositioned.

Again I am not sure what is not replicable in those software? You said it's not the font. But you have not answered whether it's the shadow, although you quoted the message.