Markdown: update is slow

Hello,
when editing .md files (I’m using qownnotes), it takes quite a time (several minutes), till I can see the result in the rendered file (FF or chromium). Actual file update is quick, it seems to be about rendering. What can I do to speed up the update?

I’m using NC 20.0.7
markdown editor (by Robin Appelman) 2.3.3
files are edited in qownnotes 21.1.3 and synced to the server.

Cheers,
Wolf

Problem still exists. It may be worth mentioning that it’s editor-independent. When using gedit, I have the same problem.