Volt data messes up exports

I was asked to change the menu name of dozens of fonts. All TTFs were shipped from MS Volt (a few years ago) after locating the exact location of the label. All I have is the TTF file, no vtp file …
So I opened TTF in Glyphs and all I do is change the font information, and export.
The correct adjustment from the volts has disappeared!
Are there any settings in glyphs (as in FLS5) to read and output volt information intact?

You should use a more low level tool to do changes like this. FontTools/TTX or OTMaster come to mind.