That Ad Insterter plugin was used by the previous owner, as you can see from the screenshot it is actually de-activated. Since I'm not using it I removed it.
Yes I'm using Ezoic WP Plugin, generally speaking I just almost left everything handled by automatic insertion.
Also WPS Hide Login has been used by the previous owner and it is at the moment de-activated. I can go on and remove it completely if you think it can somehow help, but it has always been not active, even previously.