it's a SIEMENS V23078-C1002-A303 relay. I ordered some from china, we'll see if they work.
edit: I looked at the datasheet. the relay is a DPDT, but the circuit only uses one of the switches. I took out the relay and hacked it back together so it's now using the other coil. The sunroof now seem to open faster than before, which make me think I'm right about the relay having increased contact resistance. We'll see if I have any problems with this setup (other than it being slightly too large for the case, since I didn't want to modify the relay or the board)
https://imgur.com/a/BRHfyNF