I just sent 4 photos from my iOS device to a group. Now I enter my PC on which Signal Desktop is installed and already running and a photo doesn't load, while other 3 loaded with no problem. Closing the app did not fix the issue.
Actual Result:

Expected Result:
Photo should load normally.
Signal Version:
v1.23.1-beta.1
Operating System:
Windows 10
Linked Device Version:
iOS 2.37.2.0 beta
https://debuglogs.org/f797889ef349e64c86330b2b27b1503a4ae00a0c19bee61663a47d2dec318eff
@tzs1 Are you able to reproduce this behavior consistently?
Is it always every 4th photos? What what of photos? (png, jpg, etc)
From the log there's a few 502 response codes (invalid response from server).
Later on we find updateCache: Didn't find item 1d6d919c-413b-466e-8b99-b29641483c45.
Which is coming from message_receiver.js line 555.
Additionally, there's a few: MessageCounterError: Message key not found. The counter was repeated or the key was not filled coming from libsignal-protocol.js.
Not sure which part is the root. I tried re-creating the error using the versions you specified but could do so yet.
Happened again. This time I sent a photo (iOS 2.37.0.2) and an hour later another one, which failed to render.

Debug: https://debuglogs.org/be6d241a46f0f40f767d5dffe417f5a401916140a88100159b1b47a135ee1bad
Same issue here, except that I did not send images to a group but to a regular 1on1 conversation:
Signal Desktop v1.23.1-beta.1, Windows 10
https://debuglogs.org/b767c2fbc1f1df0564e0fc279ff06226d03bd69e242b2c55819a3d39b6fdc533
Linked device: Signal Android 4.36.2
https://debuglogs.org/d2425ee6a8ba2f2974d6d2bffcb6863fc092a94878da0c76435946ae9bbcb784
The message ID for the failing image is 1553637306370.
Besides, I get no delivery status for the media messages 1553623034506, 1553631586513, which are displayed successfully. Could this be related to https://github.com/signalapp/Signal-Desktop/issues/3226? This device has, however, not been in sleep mode.
This issue has to do with a race condition between delivery receipts and attachment downloads. It will happen if you send a message with an attachment or two from your phone, and then desktop finishes downloading the attachments at about the same time as getting a delivery receipt from your contact. One update will win: either the attachment or the delivery receipt.
And we have a fix which will be released soon.
This bug has not occurred again. Closing.
Most helpful comment
This issue has to do with a race condition between delivery receipts and attachment downloads. It will happen if you send a message with an attachment or two from your phone, and then desktop finishes downloading the attachments at about the same time as getting a delivery receipt from your contact. One update will win: either the attachment or the delivery receipt.
And we have a fix which will be released soon.