I keep reading that 1/500s or faster is ideal for drone photography, especially in windy conditions, but I'm still getting soft images even at 1/250s on calm days. Using a Mini 3 and shooting mostly landscapes.

I know drones are constantly moving even when hovering, but I thought 1/250s would be enough. Am I missing something obvious here? Should I really be going 1/500s minimum for sharp results?

Any tips for diagnosing what's causing the softness?

Try using the hover function - drones can stay incredibly stable in one spot like an aerial tripod. Also check if you have any ND filters on that might be forcing slower speeds than you think. Wind can affect stability more than you realize even on "calm" days.

I had the exact same issue! Turned out my gimbal calibration was off. Try the "multiple" burst mode - take 3-5 shots in quick succession and chances are one will be sharp. Also double-check your focus isn't hunting between shots.

Are you shooting in manual focus? For landscape shots, manual focus at infinity works better than continuous autofocus. Auto focus can introduce micro-movements that cause softness even at faster shutter speeds.