I generally run 20-60 fps in Arma 3 multiplayer, averaging in the 40's and 50's, but at random intervals I get crippling slowdowns to where I'm getting 2 fps or less. The game is also at high risk of crashing during these events if excessive user input is sustained. Makes it very risky to pilot helicopters and even land vehicles, and gets me into trouble in firefights once in a while.

Does not appear to be related to heavy engine stress, as I had it happen a few times while standing guard over an hour or two, with next to nothing happening with game assets or behaviour.