Ricoh C751 text shadow

I'm running a Ricoh c751 machine and I'm having problem with black text shadow, the problem is not the same place on the paper and it's randomly , any idea what could be the problem.
I changed the the whole black unit with no hope.
find attached sample.
thanks in advance

 

I would check the transfer belt cleaning station as well as the belt itself for residual toner. Also check the imaging station blade to make sure it's no dragging or "bearding" (build up of toner)

Is it only happening in Black? Run some type in each process color, run some independently and then throw colored lines of type on a single print.

 

Thank you Biggs for your help.
I already order new transfer belt as soon as I receive i will change the new blade also and i will let you know.
Yes it makes this problem only on black color.
Thanks again

 

Also, may be for experiment sake, if available, try different brand of paper and freshly open pack. Looks like its ghosting but because only one line is affected - probably not the case. May be static. There are some limits to how much environmental and media humidity/dryness printer can handle, extreme values to either side could affect print quality in very odd ways. Also, looks like there is quite a bit of toning, unless paper brightness is so-so.
Once I had customer called me few weeks after I sold him envelope printing system, saying that he prints B/W #6 envelopes and every 5th-6th-7th envelope there would be inconsistent image density in one line, similar to what is pictured. May be not exactly like here but something similar. I was going nuts with that issue, I brought another belt, set of drums, fuser, and it would be still doing that flaw... You know what solved it? I went to near-by Staples store, bought a package of every different type/brand of #6 envelopes and guess what? All those different brands of envelopes, ran fine, without any flaws.
There was only one thing to do, is advice customer to contact his supplier and exchange those envelopes for different brand, hi did and issue never came back.

 

Thank you guys , problem solved.
I changed the transfer belt with a new Black whole unit now its ok.