Frequent Jamming of Wall Deslagger-9

We have five water tube boilers. There are 22 wall deslaggers in Unit #5 boiler. Six wall deslaggers (numbered from 1 to 6) are located in the top elevation. Eight (numbered from 7 to 14) are located in the middle elevation. Another eight (numbered from 15 to 22) are located in the bottom elevation.

Wall deslagger no. 9 located in the right water wall of middle elevation is getting jammed during retract. This problem is encountered 3 to 4 times every month. When the wall deslagger was dismantled, each time accumulation of clinker was noticed on the inner wall of the swivel tube towards furnace end. Such accumulation of clinker is not observed in the swivel tube of adjacent wall deslagger nos. 8 or 10. The root cause of the issue is yet to be unfurled. Pl throw some light on the root cause of the problem.