Vim popup flickering bug affecting Fuzzbox

[mmrwoods]

A bug introduced in Vim version 9.2.0016 causes flickering in opaque popup windows like those used in Fuzzbox.

This was partially fixed in Vim 9.2.0064 and fully fixed in Vim 9.2.0104. See vim/vim@2a74145

Please upgrade your Vim if you are using an affected version.