Cant decrypt incoming Mail if on bcc

Infos:

• Used Zammad version: 6.3.1-1721734504.b6ba68bf.focal
• Used Zammad installation type: package
• Operating system: Linux 20.04
• Browser + version: Firefox and Chrome

Expected behavior:

• Decryption of Mail

Actual behavior:

• Cant decypt Mail
• Trys to decrypt Sender → Primary Receiver