Question about Rocketbook Merger

Hello all I use my Rocketbooks practically every day. Now, after about 1 year of intensive use, I have the problem that the pens sometimes don't write properly on the page. I have already tried washing the pages with petrol. The idea was that maybe grease from my hands was causing the problem. I have also tried using classic washing-up liquid. Unfortunately, none of this helps. Has anyone had similar experiences and found a solution to this problem? Thank you