That is correct. Not just anyone can build a C4 correctly. If you have continual failures, it's more than likely because your builder doesn't know all the tricks. It's not just a matter of purchasing cool parts and slapping it together. You have to know some tricks that are common C4 problem areas. If these problems are addressed, a C4 can stand up to a lot of power.
An example: A guy builds a real stout, high rev Cleveland but doesn't do any mods to the oiling system. chances are it's going to burn some bearing at some point. If these points were addressed at the start, the Cleveland can live a long time.
C4s are the same way but if you don't know the tricks, you will continually have problems. If you get a builder that knows C4s, your problems will go away. Jay at Broader Performance is very good with C4s and can build it or sell you the parts with great tech support to back them up. Don't waste you time with TCI. PA is ok but tech support is not as good. They just want you to send them the trans.