You can’t just ask that. Not without at least taking them out to a fancy dinner first. Maybe a little dancing.

I’m sure you don’t need telling, but just in case, I would check the meta data to see when the last time the file was edited. If it matches when they sent it to you, that’s the cause.

It might be something wrong with the camera or phone they used, but the format is solid.

It’s your imagination.

Hmm, maybe they should try Linux then. Solve both the codec and the OS problem.

Leaving aside that this one is Microsoft’s fault, how is it painful? Do you even have an iPhone? And if so, how often do you move images to your PC from it, without those images going through an intermediary service?