I like a compact shotty for turkeys but for swinging on ducks especially woodies buzzin thru timber it would not be my choice. But everyone is different. Factory IC with #4s would be in my gun. Close shots you will not be handicapped with a 20ga. Pretty spot
I wouldn’t think a week between batches would matter unless u did something different. Maybe the case lube dried up or did something when sitting there for a few days that caused the weld