Component manipulation behaves weirdly and breaks the undo stack at times.

[bstordeur]

If you drag compoments (edge/verts, haven't tried faces) and cross over other components that are in the selection, TB will move the passed-over components as well. Not sure if this is a bug or feature, probably best in some situations.
BUT, if you undo your change, TB will only undo the selected components, leaving the others moved permanently:

Here's the brushes I was using, to test quickly.
compmanipundo.zip

System Information

TrenchBroom V2019.3 on Windows 7

Steps to Reproduce

Check gif.