I have never experienced this on a single player, in home computer and have not played online for more than 4 days, so take this with a grain of salt, please,
Have your server owner check the following file
Serversettings.ini
Search for the first part of this in that file
LandClaimRadiusMultiplier=1.000000
Default is 1.00. If greater than that, it could cause the new clan to claim more than expected.
There is another thread where we discussed lowering it for resource spawns (my online owner put it to 0.5 today, just awaiting server restart to take effect).
Good luck !
jim