Sentry 10 doesn't pull symbols from custom symbol server

I’m experiencing an issue on a fresh installation of Sentry 10, using the automated onpremise setup on an Ubuntu 18.04 machine. I’ve set up a “minidump” project and configured my crashpad integration to send minidumps to it (for a x86 Windows app). I have also specified a custom in-house symbol server for Sentry to use when looking up symbol files. However, even though the minidump submission and analysis seems to work as expected, Sentry never even attempts to lookup symbols on my symbol server, which means that debug information is not properly populated.

I’ve tried a variety of different things like adding my symbol server to “SENTRY_BUILTIN_SOURCES” in the config file, but while it shows up on the UI and I can select it it still doesn’t work. I have also made sure that the symbolicator docker container can properly reach the symbol server, which it can. From the side of the symbol server I see no requests reaching it at all and on Sentry’s side it just says “Symbolication: missing”. Using the same symbol server in Visual Studio works as expected.

I should note a couple more things:

  1. The reason I’m not using “upload_dif” to upload my PDBs directly to Sentry is because of storage considerations and because some of my PDBs are over the 2GB filesize limit.
  2. My symbol server is running on a non-standard port (not port 80 / 443).
  3. Sentry seems to be able to pull symbols from Microsoft’s public symbol server just fine.

I would greatly appreciate your help and please let me know if you require any additional information.

Thanks in advance,
Orfeas