[Samba] Samba lost group memberships

[Pluess, Tobias]

Hello list,
since today, I encounter this interesting problem.

System: Debian 13 with smb Version 4.22.4-Debian-4.22.4+dfsg-1~deb13u1
I am using the "ad" backend.

It works in the sense that the IDs of users can be retrieved:

id <username> returns a valid ID and works. However it takes long time for
the command to complete.
I get something like this

# id <myusername>
uid=5486(tp18v123) gid=1080
groups=1080,513,8252,103474,8319,103464,102704,1905,103074,8324,100494,10374,5505,9295,7646,10375,6022,8735,5556,8656,9158,5855,2080,8255,2089,6020,102789,104387,8627,9291,8483,7682,10456,6614,8386,10000001(BUILTIN\users)

so all the groups vanished and only their group IDs are visible.

I can use

# getent passwd <username>
and some sensible info is retrieved, it seems to recognise the account, but
also here, the group memberships are gone and replaced just by their ID.

# getent group

gives no info at all. If I try to manually mount a share with

mount -t cifs //server/share /mnt/temp -o
vers=3,user=<myusername>,domain=<domain>

it appears that the access is denied. I see in the log files errors

check_account: Failed to convert SID
S-1-5-21-1442852101-4018948630-3783845812-142435 to a UID

and

parse_dfs_path_strict: Hostname is not ours.

Where should I start looking?