Hello,
I just found that this line causes a Syntax Error in version 1.2026.8. It was fine in version 1.2026.2 (I'm using the plugin for JetBrains so I don't know for the versions between 1.2026.2 and 1.2026.8):
[[http://plantuml.com]]:Some activity;
See https://plantuml.com/en/link#27ffe93cac507589