Fluxbox version 1.3.7 (git), Ubuntu 18.04
Menu bug when using the [include] tag with a submenu in the added file:
The top submenu entry is bugged out graphicly, and sometimes the first entry
of the previous submenu is here(on the next submenu) for no reason.
Moving the submenu tag line(with end tag) to the core menu fixes the issue(only after a full restart),
but it's annoying because i need to add 3 line in original menu file instead of 1.
If you just try my menu files, you may need a full Fluxbox start (like when you login),
for the bug to show, just slides through the Submenus and watch 1st entry.
Orignal "menu" file is generated with mmaker by the way, so i just added 1 line:
[include] (/home/akem/.fluxbox/menu_extra)
Also some commands don't work when included in menu_extra, but work fine in the core menu file. And i have no idea why...
ex:
[exec] (Renoise) {urxvt -bg "#000000" -fg green -fn 9x15 -sr -st -cd "/home/akem/Renoise_3_2_0_Demo_Linux" -e "./renoise"}
[exec] (Rebirth) {wine /home/akem/.wine/drive_c/rebirth2/Rebirth.exe}
The menu bug also appear without the include tag sometimes, just adding one line in core menu file on the first entry of the first submenu and reloading the menu(without restart) makes the bug appear(and don't go away). But then just restarting Fluxbox and the bug is gone...(without changing anything in menu file)
The menu had that when the contents or theme changed, but it should be fixed ~4 years ago and in the current git master. Please try that if you can. It might cover a bunch of your other problems as well.