I experience this too but have diagnosed it to a UI issue in recent Thunderbird releases. To check if your issue is the same try the following:

1. Open the TB Address Book and ensure All Address Books is selected in the tree view on the left.

2. Open and update a contact from the list on the right. Observe that upon closing the contact via the OK button no Synchronization message or progress bar appears in the right-hand corner of the Address Book window status bar. No updates are pushed to the CardDAV server.

3. Select Personal Address Book from the tree view on the left of the Address Book window.

4. Open and update a contact from the list on the right (may be the same or a different one to step 2). Observe that upon closing the contact via the OK button a Synchronization message and progress bar appears in the right-hand corner of the Address Book window status bar. The updates are correctly pushed to the CardDAV server.

I have repeated this on Linux, Mac and Windows platforms.

AFAIK that is a restriction/bug in Thunderbird.
It only issues change events for the currently opened address book.
As "All Address Books" is no real address book, but an aggregation.
Because of that there is no matching event sent for the address book which was changed.