Strange issue with storage option SD card

[newgeezer]

In settings I chose the option to store my downloads on the external SD card. It happens regularly that this option is undone. Without changing it, in storage settings the option internal storage is marked and my downloads start over again - with the target internal storage. To solve this I tried several things: clearing cache in system settings, uninstalling the app and even formatting the SD card. After making a new setup - reinstalling the app, setting SD card as storage option - it will happen again. Any thoughts? Thank you.  

Device: Moto G7 Plus, Android 10