I've had a number of doozies, though I can't recall much specific. More than once I've bought weapons and/or cores at the end of an island and then forgot to equip them before starting the next mission. I tend to get tripped up often by wind, conveyors, and enemies bumping each other, failing to account for how the positions will change from how it looks at the end of my turn. I've lost more than one mech this way and a good amount of grid points. Once I completely failed to notice a Vek attacking a building, so I didn't account for it when deciding my turn. Recently I left a non-flying mech on a tile that was about to collapse into a chasm because I was distracted by how much I liked the shot I was able to take and just completely spaced on the environmental hazard.