Can't open glyphs file saved in older version

I have upgrade to Glyphs 3 and this particular file cannot be opened, it shows a warning like the one attached.
Can anybody help?
Thanks for your time

Can you send me the file via private message here on the forum? Or email it to support at this domain and we will have a look.

Or open the file in a text editor and check what is at line 37899.