My buddy is having the same issue with his factory OS CVR. His OS 8 glowplugs are distorting and melting the coil too. Same deal... it will keep running, but after it stops, you try to start it and no voltage can get through the plug.

This makes sense because the engine heat would keep the remaining coil glowing even if part of it is melted, and this would be enough to keep the engine going, but will not allow the coil to let voltage pass through it to make it glow for starting.

Anyway, my suggestion to him was to switch to a colder plug. This seems to have completely fixed the issue for him. Even though an OS 8 was recommended, he went to a colder McCoy plug, and this fixed it. It's quite possible that manufacturing tolerances were slightly different on his engine, and yours, and this makes for higher compression, producing more heat, and therefore more problems with glowplugs.

Of course, you're talking about turbo plugs which are different, but the theory might work for you too.