sysutils/tmux - strange behaviour with new version 2.4

[Miroslav Lachman]

I noticed some strange behaviours with Tmux 2.4.
If I run "cat /path/to/somefile.txt" sometimes part of file is missing 
in the output (no special characters in this text file, it is log of 
"pkg upgrade")

And I thing some key presses are interpreted differently. (in Vim)

I know that nobody can solve this without more details... so I am just 
asking if I am alone or somebody else have this problem too?

Miroslav Lachman