D22 head asket failure

[Hitchiker]

My D22 has just clocked "only" 180,00 and the head gasket has failed. It's an odd failure, one I've never seen before.
One shim has been displaced, and forced out from between the block and head. Apparently it's a common failure, according to the workshop I took it to. Along with that I have a cracked exhaust manifold, which is also supposed to be a common problem. Gonna' have to weld this one.
The timing chain is also worn, so the quote I got to repair everything was north of $10,000. Looks like I will be coming out of retirement (I was a motor mechanic once).
Has anyone else had the same head gasket issue? I've heard heaps of stories about timing chain failures, but not head gaskets. In the pics attached, you can see the failed gasket. The interesting point is when you look at the area of the head where the gasket went, you can see the witness marks are much more faint than those on the rest of the head. I'm guessing that the fastener in that area was either not properly tensioned, or maybe torqued well past the yield limit.
Anyone got any ideas? I'm about to rebuild, but don't want to see this fail again. I WAS expecting to see at least 300,000 K out of this engine

 

[tweak'e]

first time i've seen a failure like that. head gasket failure is very rare.
timing chains also don't wear much, and certainly not a common problem. might be getting mixed up with the yd25 engine and its timing chain issues.
worn at that sort of km's suggests oil problems.

i wonder if that cylinder has been running very hot. leaky or poor injector.
also is that broken head gasket at the front, where possibly someone might have shoved something in there and given it a smack.

 

[Hitchiker]

first time i've seen a failure like that. head gasket failure is very rare.
timing chains also don't wear much, and certainly not a common problem. might be getting mixed up with the yd25 engine and its timing chain issues.
worn at that sort of km's suggests oil problems.

i wonder if that cylinder has been running very hot. leaky or poor injector.
also is that broken head gasket at the front, where possibly someone might have shoved something in there and given it a smack.

It is a YD25. Doesn't show any signs of overheating, hardness test was OK, so head has not been annealed. It's the lower primary chain (single row) that is worn. I've never had any overheating issues, until now. Unfortunately the D22 has no overtemp warning light, and I was driving into the sun, so missed the gauge reading. Engine started to lose power, I think the management system went into limp mode. Pulled over straight away and waited for it to cool before putting water in the radiator.
It's an odd failure, you can see where the gasket failed on the closeup of the head in the first pic. As I said, the witness marks are not as prominent there as on the rest of the head.