@surfer I cannot reproduce the issue, as the savegame loads totally fine here.
As you did not indicate anything else for example the TripleA version you and your opponent use, I can only guess that you are using outdated and/or different versions of TripleA - that at any time of the game might have created an error. Also Edit Mode sometimes is not 100% error free.
It would be helpful if you created and posted a screenshot of the error message - or copy-pasted the entire error message. Also usually there is a dialogue asking you to “Report to TripleA”. Have you done that - and what did the software return?
Maybe both of you try and use https://github.com/triplea-game/triplea/releases/tag/2.7.15256 - that is not the latest pre-release, but the one I have successfully opened the file with right now.
And a friendly request for the future : Please use the TripleA-support category https://www.axisandallies.org/forums/category/28/triplea-support in the future, as we don’t want to have TripleA-issues discussed widely spread all over the game threads.
Often the topics repeat themselves, so we have one place to collect them and maybe refer to them. Thank you.