Murd

I sliced a model with two interfering parts one mesh (part) is 100% infill the remainder of the other model is 20% infill ehen it prints it does the base layer diagonal pattern opposing layer by layer but the rest is doing a side to side backwards and forward pattern which I’ve never seen before and it does this for the internal 100% infill parts and for the top layer (shell). Still has lines down as print pattern but it’s not as it was ?? any ideas? cheers