[Foot Stomper]

The C10 was likely painted in lacquer so the new urethane systems are "hotter" solvents so when in contact, the urethane solvents attack the lacquer. See picture for a personal example where this happened to me.

You can seal the pre existing lacquer coating, but this step can be tricky if you don't know what you are doing.

There is absolutely no need to strip the doors where you have no "crazing" where the lacquer freaked out. WHere you have a good result, leave it alone.

Go to your local paint supply store, ask them for their product that will seal your affected areas and respray.

The challenge you face after sanding off the crazed coatings you will have a feather edge to the paint that is in good shape. It is exactly this feather edge area that reveal a small amount of the previous lacquer paint and if you just paint it again, chances are it will craze there too. A sealer in this area will deal down the lacquer and provide an intermediate coat that will also accept the new urethane coating you are using.

Depending on the size of the areas that are crazed and your threshold for quality of job vs time and money, you may decide to strip the entire door but you do not HAVE TO strip it.

Show us pictures OP, we like pictures.