Stepts to reproduce:

1. Activate an address book in the CardDAV tab - setting is standard at "every 240min".
2. Sync.
3. Check contacts app: DAVx5 address book appears.
4. Change settings to "Sync only manually and on local changes".
5. Sync.
6. Check contacts app: DAVx5 address book disappears.

Expected result: it should stay in the list even if set to "only manually".

Tested it on

• Android 16 - Samsung Galaxy Fold 7- DAVx5 4.5.4-alpha.1
• by User: Android 10 - Huawei VOG-L29 - DAVx5 4.5.3

Reported in ticket: https://bitfire-at.zammad.com/#ticket/zoom/9545/18976

Maybe somehow related to constantly increasing IDs of address books? #1182 (reply in thread)