Hi Rex,
Yes, this is a known behavior and it is almost certainly the witness line settings in your dimension defaults, not the leader lines.
The 90mm overshoot at both ends points to the witness line "extension beyond" value. Open Dimension Default Settings and look at the Witness Lines panel: check the extension beyond (overshoot) and the gap to the node. If the extension somehow got set to 90mm instead of the usual 1.5 to 3mm, every dimension will overshoot the witness lines by 90mm at each end.
The fact that clicking a dimension makes the rest snap back to normal suggests they only rebuild when selected or when the view rebuilds. A few things to check:
1. Dimension Default Settings, Witness Lines: confirm the extension beyond and gap values are sensible.
2. Check whether the affected dimensions are static or live. Static dimensions do not update until you touch them.
3. Try View, Rebuild, and see whether the overshoot comes back after zooming or switching views.
4. Check your Archicad 28 build under Help, About Archicad, and install the latest update, since a couple of dimension display fixes shipped in later builds.
If it keeps happening, a screenshot of your Dimension Default Settings would help pin it down.
On a related note, here is a free tool that can help with scale and unit conversions: https://gad.design/scale-converter
