Before getting into building SLR coils... you need to figure out what that reason is and ideally be able to know how to determine what that reason is.
That's the biggest thing with SLRs and Mechanicals... everything they do follows some pretty simple mathematics... Nothing it does should ever happen "for some reason"... and for your own safety... you should always know what the reason is.
in my experience, there are 4 things that effect vape quality:
Wire Temp (many factors involved here, V, W, Ohms, AWG, Length, Coil Spacing, etc.)
Wire Surface Area
Juice Flow
Air Flow