pfr I have no clue, does it do the same on other terminals, or is this only on xst?
EDIT: Actually, what version of wiki-tui? The one on my screenshot is v3.5 on xterm.
I've updated the package yesterday to v4.0 and have the same issue as you on xterm 
 
Just tried v4.0 on kitty, alacritty and xst, no issues on kitty or xst, it displays as it should. The output on alacritty looks fine before entering a search but it's all f***ked-up after that. Perhaps open an issue with upstream with some screenshots to describe the problem.