unable to update group from security to Dist

Hello Experts,

While trying to update group from security to Distribution, I am getting below error.

Object ($$$$$$$: NON-TRUSTED User2) could not be saved!
Error during execution of 'OnSaving' in logic module 'ADS.Customizer.ADSGroup'.
A group contans primary group memberships and cannot be converted into a distribution list.

when I check the group in manager view it contains primary group of user accounts.

where will be this data stored in 1IM, how can we remove this entry so that group type can be changed.