Hello,
I hope this wasn't already reported, didn't find it...
For some reason my 2 rams were invisible, only their shadows were visible.
Unfortunately I have no idea how to reproduce this bug, but at least I've found out how to fix it, by inspecting one of the rams both were visible again. (probably any action with them would fix that).
I don't use any custom client, the only thing I've changed is the cam, I've typed cam ortho -f and I've been playing like that for months now. To be clear, I didn't have this issue right after changing the cam, I just mention it if it can help...