How did you get the UFOs from FL5? I’d recommend converting the VFBs directly with vfbLib/vfb3ufo for preserving most data. It won’t solve the axis issue though, as your VFBs are single master, so Georg’s advice still applies.
Jens: the ufos are 9 years old, generated by UFO Central Version 2.1b, and kerning was converted font FL style to Metrics Machine style using KERN Exchange FL/MM
I also have the VFBs, I will try your suggestion. Thabnks!