Phantom Reminders every 15 seconds

[OldElvis]

For the last 4 to 5 months my LG V40 ( on Sprint running Android 9) goes crazy about once a day, and the phone Vibrates and Audio alerts me every 15 seconds until I re boot the phone. I have tried to trcak what it is using the app Unnotification, but what ever is causing it, is not registering on that app.

Kinda of driving me crazy. Any Diagnostic ocdes I can use to find the root cause?

 

[Medstar1]

You may have to do a factory reset if you haven't already.

 

[markdoc]

Have you tried clearing the phones cache?

 

[OldElvis]

I really want tot try everything prior to doing the Factory reset first. I have not done the Phone's Cache, I will try that next. Thanks