Reproduce

This bug only occurs when using ST (the simple terminal from suckless).
To reproduce, simply put the following line in your .zshrc (sourcing the plugin in a different way might also work for reproducing this bug, but I have only tested sourcing it like this):

source '/usr/share/zsh/plugins/zsh-vi-mode/zsh-vi-mode.plugin.zsh'

Result

The cursor mode is not changing from block to line when switching between normal and insert mode.

Expected behavior

The cursor mode should change from block to line when switching between normal and insert mode.