breaks in tmux

[AAorris]

When running in tmux it looks like I get some content leaking into the terminal

It seems to happen irregularly; when pressing and holding a key, or sometimes when moving and drawing in a new cell.

This may be related to the workings of tmux, but it would be ideal to run safely by default.

Reproduction (MacBook Pro in Terminal.app):

pxltrm then move and draw (works)

tmux; pxltrm, then move and draw (does not work)