There's so many things that can affect printer performance.
Off hand it sounds like a serial connection with a handshake
problem but not knowing the details of the 6P I may be all wrong.
It can be as simple as a cable problem. Even if it's a parallel printer - some require bidirectional some don't.
It could be a memor problem -- either some bad memory or not enough.
And of course it could be a driver problem.
I also am assuming here that if you have other printers on the network that these reports print fine on those printer(s) which would eliminate an application problem.
The first step - I would think is to check the printer setup, testing it with several different configurations as possible.
It would be real handy if you could get a hold of another 6P printer that is working fine somewhere else (or test yours on another system) to try to eliminate the possibility that it is in the printer itself.
Next try cable changes.
With prices down on most printers, it may end up being mose cost effective to replace the printer (be sure and test it first with a similar but perhaps longer report).