Hi again,
I see that you are updating shape of lot of objects. In this case please do not delete the old object (e.g. school ground) but change it shape instead by adding nodes or dragging the existing once.

Alternatively you can install utilsplugin2 in JOSM and use Replace geometry function that will do that for you:
https://wiki.openstreetmap.org/wiki/JOSM/Plugins/utilsplugin2#Replace_geometry_(Ctrl+Shift+G)