XF 2.3 Promotion inconsistency and grandfathering members in

[eDaddi]

Getting some confusing feedback from a promotion I'm trying to set up.

We have an existing forum that we now want to limit access to, but I want to grandfather existing members in.

Steps:

1. Created new user group
2. Batch upgraded existing members to that user group.
   1. Sanity Check: search for users in user group = 1,179
3. Set up promotion. Promotion criteria:
   1. 50+ posts
   2. Account age 365 days +
   3. 'User NOT in selected user groups' = new user group. I assumed this would ignore or 'grandfather' in people I already added to the group.
4. Run User Group Promotions.
   1. Sanity Check: search for users in user group = 1,148
5. Re-Run User Group Promotions
   1. Sanity Check: 1,168
6. Re-Run User Group Promotions
   1. Sanity Check: 1,151
7. Re-Run User Group Promotions
   1. Sanity Check: 1,163
8. Re-Run User Group Promotions
   1. Sanity Check: 1,151
9. Re-Run User Group Promotions
   1. Sanity Check: 1,160
10. Repeating this keeps the number bouncing around, it never lands on one number

I also tried skipping the Batch User Update grandfater-in part:

1. Created new user group
2. Same promotion as above
3. Run User Group Promotions.
   1. Sanity Check: search for users in user group = 78
4. Re-Run User Group Promotions
   1. Sanity Check: 1 (my default admin account)
5. Re- Run User Group Promotions.
   1. Sanity Check: 78
6. Re-Run User Group Promotions
   1. Sanity Check: 1
7. Cycle repeats

Clearly I'm not doing something right here as I don't think promotions should fluctuate like that.

I'm on dev so criteria can't be changing by members actions.

Any thought on what I could be doing wrong?