I am having the very same problem here. The group base types and group functions (like “One ON -> ON”) of all groups defined in Paper UI are lost after each OpenHAB update. This happened to me at least four times in the past months, every single time I upgraded to a new OpenHAB version. I then have to go through all the groups manually, restoring the group type and the function.
The affected groups have different base types (Numbers, Switches, Contacts, Rollershutters). However, the items within one group are always homogeneous, i.e., all items within the same group always are of the same base type.
I am using Ubuntu 18.04 LTS on the machine running the OpenHAB server, with the Bintray respository as the packet installation source. Upgrades are triggered manually through “apt-get upgrade” on the command line.
After the most recent upgrade, I found a block of messages in OpenHAB log during the first post-upgrade OpenHAB startup. It looks as if it might be related to the issue:
2020-04-20 18:56:23.869 [ERROR] [e.internal.items.GroupFunctionHelper] - Group function ‘OR’ requires two arguments. Using Equality instead.
2020-04-20 18:56:23.870 [ERROR] [e.internal.items.GroupFunctionHelper] - Group function ‘AND’ requires two arguments. Using Equality instead.
The total number of these messages is at least in the same order of magnitude as the number of affected groups.
Thanks for your help!