Images not received in group chat, duplicate "Message-ID: <xxx>"s

[sbkaf]

• Sender Operating System:

  • iOS, freshly installed last week

• Receiver Operating System:

  • Desktop Linux v2.43.0
  • Android v2.43.0
  • Android v2.46.0 (Arcane)

Expected behavior

In a group chat 5 images should be sent and received completely.

Actual behavior

A group chat with >20 persons, 8 persons didn't received the 5 images. The others didn't say anything.
Only the first and the last image was received. Images in the middle are missing.

Analysis

Thunderbird shows all e-mails with all images.

Maybe the Message-IDs are the problem. Shouldn't they be the different?
Additionally -file names- are the same but the -images itself- are different.

Message-Id | In-Reply-To | attachment file name | received in Delta?
11111111   | 55555555    | aa.jpg               | yes
22222222   | 55555555    |                      |
11111111   | 11111111    | bb.jpg               | no
33333333   | 11111111    |                      |
11111111   | 11111111    | cc.jpg               | no
11111111   | 11111111    | cc.jpg               | no
11111111   | 11111111    | cc.jpg               | no
11111111   | 11111111    | cc.jpg               | no
11111111   | 11111111    | cc.jpg               | no
11111111   | 11111111    | cc.jpg               | no
11111111   | 11111111    | dd.jpg               | no
44444444   | 11111111    | ee.jpg               | yes

(IDs and filenames uniquely replaced in this table)

According to the sender 5 images should be visible. 10 different images are on the server.

Maybe it's connected to "send multiple images" dialog.

[link2xt]

Messages with the same Message-ID are treated as duplicates. We should not generate different messages with the same Message-ID. Not sure what Delta Chat iOS is doing, maybe it is reusing the same message object.

[sbkaf]

I could reproduce it with Delta Chat v2.48.0 and iOS 15:
Open Signal chat with about 5 pictures -> open chat media -> select about 5 pictures -> share -> select Delta Chat chat to share.
Here again, 5 pictures were visible in the recipient's chat but they are all the same which they are not.

At least on iOS 16, sharing multiple images by using the Delta Chat attachment symbol and sharing via previously selecting it at the "Photos" app works.
The first post was from a current iOS, so I guess iOS 26.

[Amzd]

Maybe I assumed a draft message object would receive an id when sent? I will have to look into this.