Indeed it looks like the foot stool is set too low. Some of them are a bit "sticky" at the top, and need a bit of elbow juice to get to the top notch. If you look on the side of the mounting from the rear you can see if that has happened. You can't easily do this unless the seat is fairly upright. Then when the seat is reclined the foot stool will be a few MM above the seat level, and flatten when your feet apply pressure.

In all situations like this (a) when it happens, start again and (b) find the oldest male member of staff and they'll fix it for you. I'm sure CIHY is a dab hand. And tje usual CWS reminder, do this first on the ground before doors closed. Sometimes CW flatbeds are defective (increasingly rare I would say now) so that could have happened here, but if an engineer is needed, or you need to be shifted to another seat, it's a lot easier to do it then. From the photo it looks like a lack of height to me since at that point the front of the stool droops a bit.