I am using a HICTOP 3DP-11, nozzle 0.4 and CURA for slicing.
I have a large print that takes 17 hrs with print speed 30mm/s, and fill 20% layer 0.2, using woodfill fillament from "bq".
or
41 hrs with fill 25%
it is 600 layers.

here's the problem.
The first time I tried to print, it stopped extruding ( and blocked the nozzle ) at a print height of approximately 21mm. ( approx layer 200 ), but continued performing its "laps" as if it were still extruding.
new nozzle and tube.
The second time it failed - as far as I can tell - at the same height. Again doing its Laps, just not extruding.

Now - between the two attempts, I have printed with the same fillament different items slicing with CURA and same settings with a height of 600 layers successfully.

I cant say exactly the elaps time at failure, just the prints are the same height, because when i checked progress the head was already some 10 - 15 mmabove the last printed layer.
Variables:
Fillament - I cannot believe it would block at the same point, a couple of weeks apart, with other good prints in between.
gcode - I have looked at this and there are no inconsistencies in the range of layers 150 - 300. and the E value on each line increases as expected.
If i think of the printer controller software - on the premise that it is not blocking, but it stops extruding:
perhaps there is a problem with the value of "E" being too big - but E would be a greater value for the 25% fill print. After all its only an 8 bit processor
Z software limits, dont think so
Internal clock - both prints were started at different times of the day, the 20% fill would have reached the fail point (print elapse time) quicker than the 25% fill print.
SD card reader - i use 8 Gb card, the gcode is 45 Mb - as it was still reading the gcode and doing Laps I dont think this is the source of the problem.
Thats it, i cant think of anything else, driving me to distraction going through posibilities.
Any help/suggestions would be gratefully received.

dennisw