[Low priority] Setting custom default (first-time-opening) zoom and position - Zoom does not work as expected

https://asthma.uni.lu/minerva/?x=2340&y=1304&submap=3283&zoom=4& Since it remembers the view in the browser I normally use, in order to check that this works I used a different browser and was switching between submaps. It does not work as expected. The zoom level is different, and when I use "-" or "+" icons for zooming, it suddenly can jump from 4 in URL to 6 while I click "-". Seems like it takes the zoom from the previous view while in fact it is a different zoom, not sure. To try to reproduce: in asthma.uni.lu switch between submaps and change zoom after moving to the next map.