Attached files are not uploaded to remote Zulip server in bridge between two Zulip servers

[mnkdg]

I've setup matterbridge between two Zulip servers to synchronize messages between selected pairs of channel/topics on different ones. Messages are forwarded fine, but uploads are not. So, if I upload file test.txt in channel on the first server, then it is uploaded fine locally and has for example the such one link : "https://chat1.mydomain.com/user_uploads/2/8e/iebjS_z4jk5uBKmQLTffd4w4/test.txt", then on the second one the corresponding message in the synchronized topic appears but with another link: "https://chat2.mydomain.com/user_uploads/2/8e/iebjS_z4jk5uBKmQLTffd4w4/test.txt" and if someone try to get this file, server chat2 responds: "This file does not exist or has been deleted.", so the file is not realy uploaded in this case.
Are there some special settings needed for attachments?