This is typical of many Chinese made compact fluorescent lamps. All of the Feit, GE and Philips spiral CFL lamps are being sourced in from Chinese factories now, and all show these defects from time to time.
The Spiral tube CFL, though small, is a remarkably bad creation. No reputable CFL factory anywhere is making them with the exception of German firm Narva. The problem on these tubes is getting good phosphor coating thickess control. If you coat the tubes before bending, the phosphor deteriorates dramatically when the glass is melted and spiralled. If you coat the tubes after bending then the liquid coating suspension falls under gravity and you get a much thicker coating on the underside of each spiral than above, it is not possible to achieve the uniform optimum thickness.
James