I'm starting to think that this is either a problem with permissions or with battery. Although I have all the permissions on default, and "dynamic code loading via storage" set to restricted, and the only permission that's enabled is WebView JIT set on "default (enabled)".
What are your battery settings? Do you allow KeePassDX to run in background? I do, and the battery is set to "optimised". See if setting it on "unrestricted" changes something.
Also, try exporting the app's settings in Settings > scroll to the bottom and click "Export app's settings". You should now have a .properties file. These are some of the settings that I have, and for me it works. It's a basic text file, so you can modify it and import it again via the settings. Open it, and see if it contains the following strings:
autofill_inline_suggestions_key=false
autofill_manual_selection_key=true
settings_autofill_enable_key=true
autofill_ask_to_save_data_key=true
autofill_auto_search_key=true
autofill_save_search_info_key=true
Other than this I'm afraid we cannot do much, as it seem many users are doing fine, and it doesn't seem connected to GOS itself. As a last resort, try reinstalling KeePassDX and uninstalling any other password manager that you might have. By the way, when you reinstall it note that there are multiple versions. I have the "libre" one, which should not have any Google dependencies; try changing the installed version and see if it changes something.
All in all, without logs, we can only speculate about your specific problem. Maybe it would be best if you asked directly the developer via an issue ticket on their GitHub. Attach them you .properties file and the log file of the app (you can find it in App info > View logs); but beware of personal data that might be contained in the logs, such as the name of your database or other sensitive settings!
If you solve your problem, you can report back here so other users that might encounter the same behaviour could try and fix it too. Best of luck.
