This has happened in previous versions of ql and was fixed for a few months but has and seems to be an intermittent problem. I have mousewheel bound to jump and it has stopped working properly since the last patch.
For a while it wasn't working at all so I changed the bind to "+moveup;wait" and it started working again. I was just playing and that bind has for the most part stopped working now, and it' not because of the wait command. If i slowly move my scroll wheel one click a second it executes the command randomly every 1-6 times I scroll. I switched back to the "+moveup" bind and it worked the same half broken way briefly, but now that doesn't work at all when I join other servers and the "+moveup:wait" still only registers a fraction of what is is supposed to. This problem is not a hardware issue, I bound other commands to scroll wheel and they register with each click just fine.
The game seems to be very fickle with what types of binds it will accept on what servers and patches, and it will accept them one second then not the next.
edit: this is a result of multiple sleep/wake states on windows. restart your computer to fix it.