Kivy. How can I fix the bug so that the buttons continue to work after several Popups?

Question

Python

The program code itself is working, it does not give an error, but after Popup is launched more than 2 times (File->Open or File-Save as button), all other drop-down menus (Color mode, Deep Learning) stop working. At first, the buttons stopped working immediately after the first replacement of the picture. Code uploaded to https://dpaste.org/cZMU#L
Python3