I haven't seen that before, but the first thing I would ask for is their "liner protrusion measurements" that they should have taken and recorded during the overhaul. (before I even mentioned about the crack) = Do they have it recorded???

Were CAT parts used? (if not, were liner flange heights measured on aftermarket liners?)

The reason some of these questions, come to mind, is that a C13 liner is a mid-flange liner, and that crack is about right in the area, where that bottom flange would seat.(just looking at picture and distance from the top of engine block)

Was "block flange" clean when assembled? (debris under liner flange)

Was "liner flange" too tall?

Was top deck of engine block excessively buffed with rotating disc pads = uneven surface? (not likely, when that engine uses basically steel head gasket)

Was reman head, uneven, for some reason?

Did part of that lower, mid-way liner seal get under liner flange, during assembly?

Were head bolt holes clean and vacuumed out, of engine block?

Does CAT have a weak area, on their C13 blocks????

Even if the repair shop can't produce a "liner protrusion record" of measurements, it could still be taken, during a disassembly, once the cylinder head was removed = you would want to be standing there, during disassembly, and watch. Might be reveling to all parties.

You should send your photo, to a CAT technical communicator, at a main CAT dealership, and see what they have to say, also.= maybe they have seen that type of C13 crack before, and could clue you in to what to look for. (if they have any past experience)