moving mails not always possible

I've in Thunderbird the settings active: "Unified Folders" as I've more than 1 Account added ( from 2 different Servers ) means:

Server A
Server B

Email Account A -> Server A
Email Account B -> Server A
Email Account C -> Server B

The issues here is now, that if I check the emails on the specific Account directly, "moving emails" is working good.

If I try to move the emails on the "Unified Folders", then some times the Emails on Email Account A are not getting moved, any how to fix it?

No file, test, or entry point is identified. Start by reproducing the move from Unified Folders with two accounts on Server A and one on Server B, then compare it with moving directly from each account. Done means messages from every account, including Email Account A, move reliably to the selected destination.

Written by the indexing model from the issue text.