Images missing from slack -> matrix

[joreg]

Since the Slack Bridging room seems abandoned and the suggested email to get help with didn't respond, i try here once again as a last resort:

We're bridging a slack room which works fine for text in both directions. But images only arrive matrix -> slack. An image sent from slack doesn't show anything in matrix.

Is this a known issue? Is there anything i can do to debug this?

On the chat someone answered: "I made that mistake in the past, the config value media_url was invalid for me. You might be doing the same." But they were custom-hosting the bridge, so could change the config files which i can't.

Any help would be greatly appreciated!