I'm also experiencing this bug. A temporary workaround (similar to the recommendations above) has been to remove the global app menu support for certain critical applications but using bash aliases.
For example, in .bashrc I have the following set up for gimp:
alias gimpfix='UBUNTU_MENUPROXY=0 gimp'
Launching gimpfix from a terminal will then put the menu back on the gimp window temporarily.
I'm also experiencing this bug. A temporary workaround (similar to the recommendations above) has been to remove the global app menu support for certain critical applications but using bash aliases.
For example, in .bashrc I have the following set up for gimp:
alias gimpfix= 'UBUNTU_ MENUPROXY= 0 gimp'
Launching gimpfix from a terminal will then put the menu back on the gimp window temporarily.