VirtueMart 4.6.4
Joomla 5.4.0
Linux OS in case that is relevant.
The comments in the files in ../administrator/templates/vmadmin/html/com_virtuemart/orders/ are causing the layout to shift and --> is appearing in the Order Edit page in the backend.
There are numerous comments and sections beginning <!-- and ending in -->
If these are broken by <?php sections then the problem occurs.
Either removing the comments/commented redundant code sections and or converting them to PHP comments sorts this out and the sections/boxes line-up "properly" on Desktop and Mobile versions.
I'm using Chrome but this seems to affect Firefox as well, I've not tested on any other browsers
Small annoyance but hopefully this will help someone.