Hey again!
I know what causes the problem, but I’m afraid we don’t yet have a solution yet: textbox doesn’t work after (or in combination with) a keyboard response. The best workaround I can offer at the moment is using mouse responses instead.
It’s a known issue though; made a ticket for it over here: Textbox doesn't register input after a keyboard response · Issue #287 · psychopy/psychojs · GitHub
Sorry for not being able to be of more help.