Invalid rendering of some Unicode characters when moving cursor

[erf]

Pasting the following and moving the cursor around, causes the characters and cursor to move in and out of view in a seemingly random fashion.

ಬಾ ಇಲ್ಲಿ ಸಂಭವಿಸು ಇಂದೆನ್ನ ಹೃದಯದಲಿ
ನಿತ್ಯವೂ ಅವತರಿಪ ಸತ್ಯಾವತಾರ 

From: http://www.columbia.edu/~fdc/utf8/

Tested on macOS, in Terminal.app and iTerm2.
vis v0.2-911-g9308e37 +curses +lua +tre

[lafrenierejm]

I get odd artifacting as well when running in st-0.7.
vis v0.3 +curses +lua