I have reverted to 1.76 to see if the recent update/s has caused it somehow. in 1.76 i can export the test mission without crashing. So something has changed (or at least, on my end) between 1.76 and 1.80 that is causing this, but the question is what?

Sadly that solution doesn't work

I have noticed that the game does not CTD when running 32-Bit. It only crashes when Arma is running 64-Bit.

In the .7z file is the two test missions I created with a single item placed into the world.

Yes, the issue occurs with no mods loaded. I'm not at my home PC at the moment but this issue from memory occurs with any mission I have loaded into the editor. I will upload it when possible.