We just figured out what cases the "boost bug", it's the fucking ragdolls. Whenever you die while standing on a ragdoll your client side collision will be permanently disabled for that player. This happens because the game disables player collision whenever your ragdoll touches another ragdoll, the ragdoll entity is actually the same entity as your entire player. You can reproduce this by killing a bot, standing on his ragdoll and then killing yourself, next round you'll have "boost bug". Also to clarify, "boost" is incorrect, all the collision from all sides will be broken, not just when boosting. By running "cl_player_ragdolls_collide 1" (sv_cheats required) it will completely fix the boost bug, but also enable collisions between ragdolls. This bug pretty much got introduced whenever Valve disabled ragdoll collisions because people were piling them on top of each other. With this information it should be absolutely trivial for Valve to finally fix this bug, it's all about just getting to reproduce the bugs.