Draft analysis and +Draft

Q1)

I have two questions. When trying to draft (+Draft1 in the FMDT) this surface gives error message. But it works when having separate drafting feature +Draft2 in the FMDT (Feature manager design tree).

Q2)

When having 0.5 draft angle (+Draft2 in FMDT) it had yellow lines. If angle is increased to 1 degree line vanished.

What is the reason for above occurrence?  

SolidworksPlastics And Mold Design