OK...... we'll take a look at this. I started your save, ended the turn... that scenario ended and I went through the campaign upgrade screens, then deployed for the next scenario and pushed units around for 4 turns then saved and when I tried to load the save I got........
I **think** gateway was originally built in slot 57 but I set it up to fit into the next available slot on the campaign list ( 19 ) so it's still looking for it's data at it's original home not the current one and this rings a bell as to why but I need time to investigate and I'm hip deep in other projects ATM but will look into this when I can