Triangular Warning Icons

Hi

I am very curious about something.

Sometimes when I do a Refresh All many of my queries show a triangular warning icon. I can to another Refresh All and no change - the triangles still show. I can go into any of the queries with a triangle and click through the steps and not get an error.

What is strange is that often if I hover over a triangle then the triangle disappears.

Why does this happen?

How do you know which Triangles identify real errors and which are false errors?

How do you prevent it from happening

Thank You