Describe the bug
When I run slackdump archive on our organization the command will eventually fail on the same channel with the following error:

STDERR 2026-02-18 00:01:33 ERROR 006 (Application Error): error in subroutine
STDERR │   conversations on stage worker: error streaming
STDERR │   conversations: Channel channel C0A0C8EM9JT: callback
STDERR │   error: not_in_channel.

This also happens if I backup this specific channel only. Using slackdump 4.0, reproducible on macOS, and also with the docker container on Ubuntu 24.04.

To Reproduce
This seems to be specific to our organisation. I have run the same version of slackdump on our organisation before, so this must be a specific item that is not handled correctly by slackdump.

Expected behavior
Ideally it would be able to continue on errors like this (maybe an additional flag?), an incomplete dump would be better than no dump.

Desktop (please complete the following information):

• OS: macOS
• OS Version: 26.3
• Slackdump Version: 4.0