TextBox2 sometimes doesn't display UTF characters

I am trying to display UTF characters using TextBox2.
Some of the times I run the program the characters are shown properly, and sometimes rectangles appear instead.
This happens with the same code, without changes to it or to its parameters.
The code is as follows

win = visual.Window(allowGUI=True, monitor='testMonitor', fullscr=True, screen=1, color=(1.,1.,1.))
display_text_box = visual.TextBox2(win, text="אלון", color=(-1,-1,-1), alignment="center", font="Arial")

I am running psychopy==2023.2.3 installed using the latest pip version, with python 3.8.
I am using an updated Windows 11 machine.

This problem never happenned to me while using TextStim, which I have used up until now to display UTF characters.
Any idea what causes this statistical bug, and how can I fix it?
For now I have found a workaround using TextStim.