yellow lines in notes

Let me tell you a story—- when my ipad got delivered it had the weird issue of yellow lines in apple notes app…I complained and after some some troubleshooting they decided to replace that…then the same issue I’ve noticed in my replaced ipad….then i visited service centre and this time they suggested these yellow line issue is happening because of my iCloud id…so i made a new one for the ipad….but last night i saw the yellow line again 🙁…..and idk it is there because my ipad is defaulted or because the notes app……let me show you what kinda lines are they