Expression evaluation error at function 'a!groupMembers': Insufficient permission

Hi,
I have a situation where I have 2 groups, one is an administrator group and the other is a basic user group.
There is a basic user action to submit a comment and upon submitting, an email will be sent to the members of admin group and basic group.
Now while a basic user adds comment and submit it, there is a process error which says -

An error occurred while evaluating expression: =toemailaddress(  a!forEach( items: a!groupMembers( group: cons!HS_ADMIN_GROUP,      direct: true,      memberType: "USER"    ).data,    expression: user(fv!item, "email")  )) (Expression evaluation error at function a!groupMembers: Expression evaluation error at function 'a!groupMembers': Insufficient permission).

FYI - Process model security --> Admin group - administrator access, Basic user group - Initiator access.

Can someone help me fix this issue.

Thanks in advance