How to debug TTF export error (There was a problem converting the PostScript source font)

I have run into an error that others have faced in the past when making a somewhat complex series of characters. When trying to export my font as a TTF or OTF file, I am running into “There was a problem converting the PostScript source font (Regular)”.

Based on suggestions from previous topics, I have unchecked “Remove Overlap” and “Autohint” in the export settings. In the Font Info > Instances I have enabled the custom parameter “Disable Subroutines” and disabled the custom routine “Autohint”. Yet I am still seeing this issue.

I had managed to export a TTF back in September or October, but now I want to export a new version with a few tweaks.

Is there a better way to identify where the problem is coming from?

Try the latest beta please. Go to Glyphs > Preferences > Updates, activate both checkboxes and press the Update button.

The behavior on v2.6.4 exports fine. Thanks for your response.