Sometimes it doesn't work if you have high ping (internet / connection) lags. The higher your ping is, the longer it takes until a command gets sent to the server and the action happens.
So, simple explained: If you have high ping = stuff needs a few seconds or longer.
Check your ping next time something like that happens, then you can be sure it was caused by that.
Maybe you just pressed the wrong buttons or didn't press them correctly. The default keys are "Shift" + "X", but you can change it in the settings in garage or under F11 in freerun. I recommend to use only one key instead a combination.