Rare problem with Admob


Hi tried my New App in somes friends phones.
In my phone LGk10(2017) and in a Samsung J7 it all worked good, but in two Samsungs A7 it freezes the APP.

The thing is that i push a button that opens an interstitial ad previously loaded (first time in screen initializes) and then when user closes the ad it perform a new load of instertitial and then another things in the game (it gives the user some help in the game)

The blocks are these:


In all the phones it showed the Ad, but in these with Android 9 when i click to close the ad, it returns to the game screen, but it freezes(before executing the game action asociated with the ad; the screen its a little darker, like when the cellphone is strating to shut down screen). The game doesnt respond at anything; phone its ok.

I tested in 2 Real samsung A7 from two friends and also in appetize in all the phones.
The crazy think is that i have also a RewardedVideo and this worked well, also with android 9.

Its important to say that all of these is with Test Banner Ads, because my admob adds are not showing (maybe related with something with SDK and actualization of AB) but i have a doubt. Yesterday i testes my app and i always getting this same AD

But now, im getting that ad,and other ads real ads, in between the google test ads. Is this normal?

By the way, did anyone used this online test platforms with real android phones?
I read that is a firebase test lab with real phones, and also i have heard about other webs as appetize . Do they work well?