On configure a new CYBERNET Panel PC with Win10, I experienced the similar issue (ie some widgets are not shown after some screen activities until switched to other app Alt-Tab, or click onto some other buttons in the app), it doesn't happened on a development CYBERNET Panel PC. After create a new user, install the same Python 3.9.12, the same kivy 2.2.1 the issue still exist. Until I found the Graphic Driver is different. It was 31.0.101.3222 Intel Iris Xe Graphics 11/07/2022. After update to 32.0.101.6083 2/10/2024, the issue disappeared. Hope this useful for someone in future.

ps I am surprised by a new PC in 2024 is installed with a 2022 Graphic Driver :p