Brother MF 9420CN is asking for troubleshooting and... (by 12 users)

My MFC-9420cn is demonstrating the same problem. At first I thought it was because the "parts life" indicated that "PF Kit" life was down to zero.
The Users guide did not help at all. After considerable on line research I found that the PF Kit is only on machines with the second paper tray -- so my machine did not have a PF KIt. I went to the trouble of obtaining firmware update "version j" and installing it It did convince the machine that there was NO PF KIT, but did not solve the problem. Next, I replaced the OPC belt I was using with one that I bought recently which makes streaks. I had spent over $300 in response to the message which said "Replace OPC Belt cartridge but the new one started making streaks after about 300 pages, so I put the original back in - [it made white marks on a color picture -- but I can live with it ]. When I put the defective [but low page count] unit back in, the message seemed to have stopped. So I have 4 choices: 1) use old cartridge - run a few pages, get message, turn off for several hours, start again; 2) run with newer OPC BELT, get horrible streaky pages and faxes I can't read; 3) Spend another $300 and hope I get a good OPC BELT. 4) try to figure out how to defeat the page count feature on the original OPC BELT cartridge. I cannot find any phone number or email link to complain. I feel that this machine is a joke on the public. SHAME ON BROTHERS. I HAVE BEEN MPCed.

brother mfc 9420cn machine error 21 ? thankyou

brother mfc9420cn factory reset

brother 9420cn machine error 21?