Editor breaks level tag

[FountainMapper]

I was confused by a maps.me commit and isolated an issue with the "level" tag.
I searched a POI with multiple levels. When I started this bookstore HAD two levels
http://www.openstreetmap.org/node/1507184560
...
level=0;1
...
I added opening hours with maps.me and waited until the update was applied to OSM. Now the POI looks like:
...
level=0
opening_hours | Mo-Sa 09:30-20:00
...
Opening hours are added. No problem with this. BUT the value of level was modified. It was not even visible in the maps.me app. So a user accidently destroys the value by editing the POI.
Check out:
https://wiki.openstreetmap.org/wiki/Key:level#Multiple_values
As far as I understand, the original value of the POI was valid. Even if it would be invalid, maps.me shall not touch the level-tag, especially without any feedback to the user!

I guess every edited/added tag causes the behaviour. This is not specific for opening hours.
Version: 9.0.1-Google
Datenversion: 171208

[nrenner]

Potential cases in Germany as determined by this AWK script using the changesets dump and a full history extract:

• objectID version, timestamp, key=  (Deep History, History Viewer; MAPS.ME version)
  old value
  new value
• n1069303536 v10, 2017-10-07T08:37:30Z, level=  (DH, HV; ios 7.5.3)
  0;1
0
• n1507184560 v5, 2018-01-07T22:35:09Z, level=  (DH, HV; android 8.0.1-Google)
  0;1
0
• n2069302320 v4, 2018-01-07T09:37:52Z, level=  (DH, HV; ios 8.0.1)
  0;1
0
• n3823139978 v6, 2019-08-19T10:23:55Z, level=  (DH, HV; android 9.1.8-Google)
  1;2
1
• n5771189137 v3, 2019-08-02T15:24:43Z, level=  (DH, HV; ios 9.1.9)
  4;5
4
• n5844370749 v3, 2019-05-23T04:10:14Z, level=  (DH, HV; android 9.1.5-Google)
  0;-1
0