Temperature too high. We keep it down to 254. The higher you go the faster and more this will happen. If it were an invert problem you would have crystallization problems, which you didn't. Cooler temperatures mean a little more stirring, but less unbreakable clumping. Lower temperatures allow you enough stir time to successfully break up those clumps. At higher temps those clumps are like rocks. We take ours to 254 plus or minus depending on the syrup and weather. We stir immediately after boiling and then immediately it gets pushed through a screen. We can get 100% through the screen this way. If temps are higher we will have a percentage that will not go through. The higher the temp, the less that will go through. We are pushing, smearing it through the screen, not just shaking it.
shrunken producer, from 8,000 taps to 4,000 to 5800 to 9500 to 11,000 vac
5x16 woodchip fired evaporator with 5x10 max flue and 5x6 revolution front pan
CDL 20+ RO
Double 10"filterpress
sp-11, bb2, airtech L63, L160, L230 vac pumps
CDL low profile electric releaser
MES 8000 electric releaser
CDL 4000 tap mechanical releaser