Game crashes on weapon swap

Playing a Mercenary (Witch hunter) build that uses separate weapon sets with the same crossbow, left click shooting whatever ammo is loaded for weapon set 1 and right click for weapon set 2. Bug occurs after about 10 or so minutes of initial game play while going from left click (galvanic shards on set 1) to right click (plasma blast on set 2). Bug doesn't occur immediately after starting game but is reproducible 100% of the time (so far) after about 10 or so minutes of playing, with or without loading screen in-between.