Nondeterministic output?

I wanted to add a startup message for my terminal and colorize it with gay; however it appears gay may have some nondeterminism in its output?

Here's an example:

And here's the file used in said example:
woof.txt

I have verified that this happens with other inputs, such as simpler inputs that don't use any fancy unicode, etc.
I have verified that this problem occurs in kitty and alacritty; it seems the common denominator is gay.
Also, this happens for any color scheme, not just -t.

EDIT: Okay so using the interpolation option 2d "fixes" it, though it's still not entirely deterministic:

[interdisziplina]

See this function: the period and interpolation can be set via a command-line argument or is else chosen randomly.