According to the customer's description we reproduced the issue following the steps below:
1. Vanilla installation fo IDM 6.5 + PostgreSQL 10
2. Created a test user (tuser1) and added itself as its own manager
3. Could access the the user (Manage -> User -> tuser1) with no issue
4. Upgraded to IDM 7.0.1 (and upgraded existing Repo)
5. When accessing tuser1, 500 Internal error pops up and is logged also to console and openidm.log
6. Tried to create a new user (in IDM 7.0.1) with itself as its own manager, and although it was saying that change was successful, it did not update.
Customer said that they experienced the same issue in their test environment also.