Hi Lars,
I'm not aware of any issues. However, I recently got caught out with summary panel customisations not behaving how I expected. . . . .
For any task UI customisations to take effect, the person who is assigned to the layout template must also be assigned to the task where they are using the summary panel. The orange "important" box on this documentation highlights the behaviour.
Not sure if this is the same as you are experiencing, but this tripped me up recently. I expected that if you have a layout template assigned, the customisation would take effect when viewing any task. Apparently not, you also have to be assigned to the task for the customisations in the layout template to take effect.
Best Regards,
Rich.