IBM 4247-003 printer starts printing and then slams code 056

[landspeeder]

I have this printer that I put a new print head in, bent pin, and blew it out and checked the adjustments from the downloaded service manual and sometimes it prints for quite a while and other times it starts to print and then bangs into the frame (left)....I tried to flush the carriage homing sensor...no diff

What might be the most common issue and the guy wont pay for the P/H if it doesn't work and I cant send it back!

Thanks ya'all