Ridge of debris under vinyl liner

[SheldonC]

I noticed an issue this year, where a see a line (ridge) in liner, running from one end of my inground pool to the next. It is an elevated ridge that sits mid height up the wall. At first, it looks like the wall has a long crack. After pushing on the ridge, I can tell it is dirt or gravel. It seems to be coming from the top, because i feel particles coming from the bead down to the ridge. In fact, below my skimmer, the wall is smooth. Suggests that dirt is coming from top down. I also see this ridge on one of the ends of my pool. So a full 34' length and a 16' length. I have the pool installer coming out next week to take another look. Pool is 4 years old. Customer service on phone is saying that it is normal ground water from the bottom. Telling me it is impossible to come down from the top. However, i can tell it is definitely coming from the top, through the bead. I am unable to find this condition online. Has anyone heard of this?