Artefact while painting on 3d model

[#1]

Hello when i am painting on the 3d model i have this issue where in projection mode or even when i merge down a painting i adid on top . in the transperent edge it will create this weird atefact all along the stroke.

I dont know what to do . 

cheers

[#2]

Hello when i am painting on the 3d model i have this issue where in projection mode or even when i merge down a painting i adid on top . in the transperent edge it will create this weird atefact all along the stroke.

I dont know what to do . 

cheers