Markdown: update is slow

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.