When using the “Combined + Rune Selection” Keyboard & Mouse control scheme, the “Rune Attack” keybind will also function as an Interact key, which can lead to problematic moments where your character suddenly has an urge to harvest resources in the midst of combat. This issue does not seem to occur with Runes that cost stamina.
My interact key is E. I did a bit more testing and it seems to be more specific than just runes that cost focus. For example, this bug occurs when using Lightning Blast and Lightning Leap but not Lightning Storm or Inferno. No change when resetting my controls.