tmux triggers beakdown in Unicode parsing

In tmux, if you're viewing a window smaller than your current screen size, it pads the screen with various characters, something like this:

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Frequently this sort of text triggers a breakdown in the utf-8 parsing in a-shell, causing the screen to fill with garbage:


This is the clearest test case I can get. Tmux not involved. If I just take the above blockquote, put it in a file, `less` that file, then press ctrl-r over and over, the glitch comes in and out. This is straight in the a-shell shell's own less, not logged into any servers or anything.

This unfortunately makes a-shell virtually unusable for me, so I hope this is something fixable.

thank you,