Strange Cell Damage on off-grid Panel

[Sloflyer10]

I have a single mono-crystalline 72 cell panel which charges batteries through a ProStar-15 controller for a sliding gate operator. It has been doing this for about 5 years now. When I looked at the controller display recently, I noticed the panel was generating less than half its usual current in full sun when charging the batteries. I took a closer look at the panel and some of the cells in the panel have these strange marks going across them(see attached image). About 2/3 of the cells on the panel have these marks. I can only describe the marks as looking like someone had dragged a hot soldering iron across the cells although I know that is an impossibility with the glass over them. I thought maybe water intrusion into the panel caused these marks but a lot of these marks are horizontal across the cell and I would think water dripping down the cells would have a more vertical orientation so I question if that is the cause. There appears to be absolutely no moisture within the panel. It’s been a year or two since I last cleaned the panel and I don’t remember seeing these marks the last time I cleaned it. I am pretty sure I would have noticed them if they existed then. Does anybody have an idea what is going on here?
CellFailure3.jpg

[Sunking]

You have Snail Tracks. Look it up. Time to buy new panels.

[Sloflyer10]

You have Snail Tracks. Look it up. Time to buy new panels.

Thanks Sunking. I found a number of articles on Snail Tracks as well as Snail Trail. Curiously, they draw different conclusions as to what's causing them from cracked cells to deposition of foreign material on top of the cell. There is also a divergence in the harm they cause from "it shouldn't cause the output of the panel to degrade" to "there may be up to a 70% degradation in output". I wanted to find out the specific cause of the problem for my 5 year old panel before I throw a new one in there and have it do the same thing

[Sunking]

No expert on Snail Trails, but I know what they are, how they get started, and what they can do. Your getting mixed signals because you are hearing is from individual cases. For example in your case you are experiencing power loss. While others have noticed no difference on the short term.

What causes it is a manufacturing defect like a compromised seal that lets moisture. Apply moisture, heat, sunlight, and UV radiation and cells become detached to the bonding substrate. This develops cracks on the silicon glass cells which can then lead to a fractured cell over time.

If you bought them in the last few years and still in the Material Workmanship warranty period which is usually 2 to 5 years, file a claim.

[Mike90250]

as Sunking says, Snail Trails gets my vote too.

[inetdog]

as Sunking says, Snail Trails gets my vote too.

My only observation is that the pictures of snail trails that I have seen do not have the long straight lines that show up in the photo, so either this is a different kind or there may be a mechanical stress contribution (either in fabrication or installation) that has forced the trails to follow straight lines.
Unfortunately for the OP the trails appear to cross most of the panel so the bypass diodes will not help to minimize current reduction, as they would if the damage were limited to one bypass segment of the panel.