Admob Problem - invalid traffic

Hello everyone, it’s been several months that in my profile report I see the item “invalid traffic”, the top came last month when the amount was totally deducted from me as you can see

I have read the admob guidelines, but they all refer to “anomalous clicks”, made on purpose on banners, but this is not my case (at least not on my part).

Are there any other reasons why this can happen? Does the lack of “app-ads.txt” affect?