Typing fast causes missing frame

While testing pmaports!1625, I'm seeing that when I type a password quickly, sometimes a frame is missing.

For example, I would type "asdf", and it would not draw the third circle for the d character:

Typed in	Displayed on screen
a	*
s	**
d	** (missing frame! it should be ***)
f	****

CC: @ell1e, you fixed a somewhat related bug in !91 (merged), any pointers or possible fix?

CC: @craftyguy

EDIT: tested on the pinephone, postmarketOS edge