When I was creating a Japanese font, I have found an issue that the 'Has
Vertical Metrics' flag turns unset every time I load the SFD, although
property is recorded into each glyph in it.
How to reproduce:
1) Create a new SFD with 'Unicode BMP' encoding.
2) Create a glyph at U+30A8.
3) Check the 'Has Vertical Metrics' flag in the font information dialog.
4) Set vertical advance height of U+30A8 to 800, or whatever except 0 or
5) Save the SFD and exit from FontForge.
6) Make sure that 'VWidth' is recorded, using 'less', 'vim', or
which you can read a plain text.
7) Open the SFD with FontForge and open the 'General' tab of the font
8) Check if the 'Has Vertical Metrics' is checked.
'Has Vertical Metrics' checkbox is checked.
'Has Vertical Metrics' checkbox is UNCHECKED.