Film Coating problem

I wanna a suggestion from all validation expert. we have a hygroscopic drug coating with opadry with solvent (IPA& Methylene chloride). But there is problem regarding LOGO INFILLING and Surface erosion on the tablets.Flow rate of coating solution is about 50g/min/gun. there are two gun on the coating machine. Automization pressure is about 0.15 to 0.2 mpa.Gun to bed distance is about 16 cm.coating time is about 86 minutes with no weight gain.
Can all of you pl. suggest what was the reason of logo infilling. What will be remedy for that.

Have u checked the Pan RPM ? pls try it with different RPM and check