FH 12 piston problems

I am having serious problem with a 1994 FH 12 with a D12A engine , it came into the workshop blowing water out the radator I removed the cylinder head and found a cracked liner and piston . I replaced all the liners , pistons and big end and main bearings inchassis after 1 day it died again this time on a diffrent pot . It has good oil pressure doesn't overheat but the pistons look like they aren't getting oil from the cooling jets they are not blocked and are pointing in the right direction . Has anybody have any ideas on where the issue is

 

I removed all the cooling jets when I rebuilt the engine the first time and cleaned them they where not blocked , it seems like there is a relief valve or restriction in the oil galleries to to the coolers
Thanks for your ideas