The same happended to me, bouncing a grenade to myself.

The fact is that the XML has no errors. After I made it, I checked it, then checked again, but it's alright. I think it's something to deal with the code instead: Happens when returning to certain maps, the entities go crazy, specially the ones added with xml rules, but only referring the current level. Example: After returning from C&M and killing the overspawn soldier, the Viper which picks you up before suddenly flashes throughout the level, in some points. So do the teleporter models, bullets, and shards when returning from Rfth. It's the xml files, but from the current map only, and they're triggered somehow only after you return.

Hope you get what I mean, now.