Undo/Redo not working for a Tkinter text widget

Question

I have code for a tkinter text widget using tk and ttkbootstrap: (part of code)

usertext = tb.Text(frame,width=95,
     height=24,borderwidth=textandlineborder,wrap="none",autostyle=False,undo=True)
usertext.grid(row=0,column=0,sticky="NSEW",pady=0,padx=0)
usertext.configure(autoseparators=True)
usertext.configure(maxundo=-1)

However, when I try using Ctrl + Z or Ctrl Y, the caret (text cursor) moves around, but the text stays the same. It doesn't undo/redo the text at all, but the function is called. What could be the root of this issue?

(My code is very long so I can't upload it all, if there's any other data I should provide just ask)

I tried changing around some values and stuff but it still didn't work.