Just fixed a flat on my bike which, like that one, came from the tire liner chewing through the tube. The holes are above the raised 28″ molded into the tube, at the upper-left corner of the tire liner impression.
In this case, the tire liner (which, judging from the color, was a Slime) was too short by maybe 50 mm. This view inside the tire shows a 10 mm gap where the ends didn’t overlap as they should:
I don’t trim the rear-tire liners, but comparing a handful in the drawer shows that the as-sold lengths differ by a few tens of millimeters. The Marathons are husky tires, but the tread OD isn’t all that much different from stock tires: that’s the definition of a 700-series tire.
That we’re getting repeated flats from tire liners intended to eliminate flats is, mmmm, disturbing. Looking at the condition of the tire treads, however, shows we’re not getting an order of magnitude more flats from road debris, so it’s a net win. I doubt we could get through a month of riding without a flat; I replace tires when the carcasses accumulate enough gashes that the tire liners begin extruding through the tread.
Also, remember that these samples come from three bikes that travel upwards of 2000 miles a year (each!), not just one bike ridden along a nice rail trail on weekends…