No other games present this issue, just ioquake3. Even OpenArena (installed from repository) doesn't presents this issue on ioq3 1.36+u20140116+gdde36d9-1/Ubuntu linux-x86_64 Jan 18 2014.
I can reproduce the problem playing on maps such pro-q3dm6, where you get high speed strafes during heavy fire... (downstairs on red armor to shotgun, trickjumping railgun to rocket bridge, rocket-yellow-middle positioning, etc...).
In these situations almost everytime I get teh binds for forward and shot stucked. Sometimes firing and sometimes simply doesn't responding to keypress.