Our Toshiba e-studio250 copy machine is leaving a

https://www.tonergiant.co.uk/blog/2017/05/black-lines-down-the-page-4-causes-and-how-to-fix/

Sadly, the poential fix is a step by step process where each step either solves the problem or doesn't thus forcing you to move to the next step. The procedure on the above listed page includes cleaning, which you indicate having performed. Each time you try to print, you undo your cleaning in this instance. Look for advice for your specific model of printer. Toshiba has interactive tutorials. https://tbs.toshiba.com/tbs/support/#downloads
https://www.atechnj.com/what-to-do-when-your-printer-leaves-black-lines-or-smudges-on-paper/

Get an inexpensive toner vac if you are cleaning a spill. If the pages are coming out of the machine with toner on them can you post a pic?

replace the black image unit

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

It could be leaking toner from the recovery area that sis on top of the dum, it removes any toner that was not transfered to the paper. You would have to remove it and empty out the toner.

clean d parer feed rollers if not repaired then clean d pcu

I also had this issue, waste tone was comming from the transfer belt, had a good clean out been good for months now.

make sure paper guides are secure other then that could b dirty optics (mirrors under the glass) or drum / fusing unit

This is the test to determine toner or fuser issue.
Print a test page
When you hear the paper feed into the machine open the top to stop the machine
Remove the toner cart.
You should be able to see the page with printing on it. (This is before the page hits the fuser)
If you can see the smudge or marks on the page the problem is most likely the cartridge but NOT the fuser.
If the page is clean the problem is most likely the fuser.

A smudge across the copy can be in many different areas.
Some ideas.
The drum cleaner may be the problem as you indicate.
It may be a piece of paper ripped of dragging across the surface of the paper causing the smudge.
Also the fuser roll coating may be very worn and causing that.
One thing to try that can show you if the defect is on the drum cartridge, is start to run a copy, After the paper feeds and this is timing, shut the machine off when you think the paper should be about half way through the copy cycle, then see if the copy defect is on the unfused page, If it is smeared before it reaches the fuser, it is in the cleaning section, if it is not smudged, then it is most likely the fuser rollers are needing replaced.
First look for a paper fragment in the path, step 2 is to shut the machine down in mid copy and see if the defect is there.
The fuser is the hot area of the machine in the exit area, If you can take a flash light and look in there and see if you observe wear or heavy toner buildup on a roller then obviously thats the problem.