It is estimated that the printer is a little dirty after a long time. When I opened the printer panel, I saw a metal rod. Clean with 20 # engine oil (for sewing machines, not cooking oil) and a soft cloth. The more oil, the better. When cleaning, turn off the printer and keep pushing the needle to clean all corners. Oil must be injected. A4 paper can be printed, because A4 paper is thin and the needle resistance is small. In this case, it can be cleaned. Generally, there will be no problem around 1 year, depending on the use environment.