I’ve actually been experiencing this consistently since the Fine Tuning patch release. I’ve encountered it with Proxy, Fletcher, Nader, and Sparks.
I’m really not too sure what’s triggering it, but it seems to be associated with mouse1. If I left click shortly after any repeatedly usable ability (and even sometimes if I don’t, though less consistently) my Merc will begin spamming that ability, sometimes impossibly so. For example, as Proxy more than half the time I throw a mine I will simultaneously throw two. This has the interesting effect if I’m backpedaling of leaving a nice trail of my mines to me, and if my intention was to immediately shoot that first mine, or if a stray enemy explosive goes off near the it, then I end up exploding from the chain reaction.
As Fletcher I have on several occasions pressed the sticky bomb button once, and without any further input from keyboard or mouse, I have watched him throw another two in rapid succession. Switching weapons can interrupt this.
With Sparks the medpack animation sometimes doesn’t convey the multiple ability activations, but i’ll see my ability charges go down more than once and find that I’ve been throwing health kits by twos and threes.
Nader is especially bizarre. I don’t think I’ve had the issue of the grenade launcher continuously firing without input from me, however I’ve had abilities activate automatically on death. Martyrdom often activates itself, but more interestingly if I had been using it my grenade launcher activates at least half the time on death and sometimes twice. The launcher grenades don’t launch anywhere, they just sort of appear right there at my body. I’ve watched closely, and had a lot of deaths to observe, and I’m pretty certain of what i’m describing; Martyrdom’s animation is different enough from a launcher grenade, and the damage from a launcher grenade isn’t a guaranteed finisher. I’ve also made sure these aren’t just hostile Nader’s grenades. So with the full effect of two launcher grenades appearing at my death, and then me activating Martyrdom, I have on multiple occasions dropped THREE grenades at death. It’s also kind of annoying that I involuntarily explode in front of medics trying to revive me all the time.
I’ve checked and rechecked my keybinds, and they are set to default. I have never encountered any anomalies of key activation with my keyboard in any other game I play, or in any of the thousands of words worth of school work. Even if I were to spill water on my keyboard and have a few dozen keys registering simultaneously every time I pressed anything, it probably shouldn’t give me super powered martyrdom.