Weird glitch/corruption editing Arial typeface

Hi there,
I’m using Glyphs Mini, and am attempting to edit the Arial typeface for a client (who requires infant style ‘a’ and ‘l’ characters). I’ve edited this across Regular/Italic/Bold/Bold Italic versions, but when I try and export these as OTF, they get corrupted. Only the Regular Weight Italic exported without issue, and even then looks corrupted if you reopen it with Glyphs.
The others vary in success, some I can reopen the .glyphs file, but can’t export. With others, the .glyphs file gets corrupted after the first save and I can’t reopen it “The file is corrupted. You can try to fix it in a text editor.”

My first thought is that maybe I was editing a system version of the typeface, but I don’t think this was the case as all four weights of Arial were TTF files.

Thanks in advance

There is a bug in the current version. It will be fixed in the next update.

Can you send me the .glyphs files that you can’t open any more?