This happens to me some rare times with my basic NGS optical USB-wired mouse on Linux. It could be an aging hardware (some micro-cut in the "holding" signal?), or a rare bug. Usually, releasing button, waiting a second, and aiming again is enough, but I believe it happened once when it repeated the bug several times in a row.

Although I can't say that there never is any malfunction with this aged mouse, it could be worth asking devs for the conditions when the game can shoot arrows so rapidly (micro-cuts, really?, or a flaw in the I/O methods?), and eventually put a safeguard in the game. I will report on Bugtracker and provide a link to here.