"Notice Detected corruption of the game state. Game was not saved to prevent corruption of your save files"....and send the game to the forums so they can fix the problem.
After I have 2 or more Receivers and save or autosave while the beams are active. Saves okay if I save during that 1 second that they're off.

Ooh, that's quite a nasty one :(

I suspect it's to do with the new beam code, but I haven't had this error myself and I've been using multiple receivers and saving/loading regularly; can you give me some info --

a) Are you receiving from ground-based or orbital transmitters?
b) Are you using the personal microwave antenna equipment or just normal receivers?

Also if you could send me your mod list and save file that would be really helpful. It could be another mod interfering somehow.

I just disabled all mods except Portals.
a) ground only
b) removed personal microwave as I thought it was the problem
So I did some experimenting..starting a new game, no modes but Extended Picker.

It's got to do with the range of beam after ~650 tiles distance; 1 tile farther, it gives error, 1 tile closer it's fine.

Did you want the new savegame test? Email?

Ah, that makes sense. I should be able to reproduce this - I didn't test these distances (but it did occur to me there might be some limit).

I'm probably going to change the beams so they only extend like 10-20 units from the source and target. But I'll report this as a Factorio bug also; save game corruption really shouldn't happen!

Also it means orbital transmitters should always be fine, as they extend exactly 100 units vertically.

Thank you for the detail and for discovering the cause!

Just seen the forum thread, looks like it'll be fixed in the next Factorio release, thanks for reporting it there!

Eh? I didn't get as far as reporting elsewhere. And sorry I forgot to mention; fun mod!
https://forums.factorio.com/viewtopic.php?t=50758
zebediah49 is to thank for that.

Oh sorry, just assumed it was an alias. Anyway thanks for the feedback, glad you enjoy it!