Found in PINES 3.2.X production. If you enter the "Edit" screen within a patron account, then click "Patron Search" in the upper right and retrieve another patron, the Patron Stat Cat values that were present in the previous account are filled in on the new patron's screen. If you save the new patron without changing those values, they will be saved in the new patron's account. Steps to test on current master:
1) create a patron stat cat in Administration -> Local Administration -> Statistical Categories editor and assign multiple entries (at least two) for CONS or the branch unit where you're logged in.
2) open an existing patron account and assign a stat cat value (Patron Stat Cat).
3) retrieve a new patron using the Patron Search button in the upper right.
4) confirm that the previous patron's values are entered in the Patron Stat Cat field.
We've learned that refreshing the screen in the browser controls removes the value, but unless you know that or are paying careful attention, it will enter undesired data upon saving.
Evergreen 3.2+
OpenSRF 3.1
PostgreSQL 9.5
Ubuntu 16.04 LTS
This is still a problem in 3.4.2. The patron stat cat field is so sticky that it carries over from one patron edit screen to the next patron edit screen.