I've run into a curious problem just now. I deleted my cache files after suggesting someone else to do the same, and was unable to join the game afterwards (the other person rejoined just fine). The game would stay on the ad screen indefinitely, with no further communications with the game server (it wasn't silently downloading anything in the background). I did a bit of troubleshooting to try and fix this, and here's a list of things that didn't work:

1. Tried joining the game both from the hub and using a direct IP link.
2. Reinstalled byond and rebooted the PC.
3. Switched from 515.1608 that I was running at the time (I downloaded the 515.1608 installer for step 2) to beta 515.1609 and stable 514.1589.
4. Pressed the "Clear Cache" button in byond preferences, which, in hindsight, I probably should've done before deleting the .rsc.
5. Deleted all mentions of the game and its hub from different cfg files in byond's folder.

Trying to join other games would initiate downloads for their files, so it was that specific game refusing to work. Now, the game that I was having trouble with is something that I often open in DM and host locally, if that has something to do with the problem, because it did help with a solution. I did find two ways to make it work again, but neither method is direct enough to my liking.

The first time, I hosted the game locally, and it worked without issues. Afterwards, I could join the online server from the hub, too, despite them running different builds of the game. Of note is that, after this, byond's cache folder had byond.rsc and byond1.rsc files in it, when before was just one byond.rsc.

After that, I deleted the .rsc files again, and couldn't get it to work again until I joined a different game and downloaded its cache files. After that, the game that I was having trouble with initiated its own download as normal. There is a single byond.rsc file in the cache folder right now.

Is this a common problem? I recall nuking .rsc files before without it breaking anything.

EDIT: I have since used the Clear Cache button with some cache present, and it doesn't seem to trigger this problem, so I guess that's another way to go about this. Probably the intended one.