I've noticed with every plane, that when there is blue sky, there is flashing similar to lightning. It's always near the top of the screen. One day they were about six seconds apart, the next day about seven seconds apart. I'm using FSX, ASN. Everything else is running very smoothly.

When I used ASE, I had this problem.  It was an acknowledged problem that occurred when you had ASE in "standard" mode and it had something to do with ASE and simconnect.

 

But since upgrading to ASN, I have not seen it.  ASN was supposed to have completely resolved this issue which, for me, it did.

 

You might want to contact HiFi Technologies on their website.

I see this behaviour in p3d2.5 i use asn for weather