P0025, P0024 & P0019 error codes 2007 C230

Question

I had the "Check Engine" light illuminate and took the vehicle to my mechanic. The faukt code was P0025 - Camshaft position error, exhaust over-retarded, bank 2 (Driver's Side). The mechanic checked the camshaft position and it was correct. He reset the system and the check engine light went out. Check engine light returned a few days later - same error code - P0025. Mercedes Forum research indicated one possible cause could be the camshaft position sensor. I purchased and installed a new camshaft position sensor but that did not resolve the problem. The next potential cause indicated was a bad magnet assembly - this was replaced and again, the error code returned after being reset and driven. The codes currently being stored are P0025, P0024 and P0019. Additional research indicates the possible cause could be a defective Balance Shaft and there are at least two class action lawsuits mentioned related to this problem as the repair is very expensive (.$4,000?) as the engine has to be removed to replace the balance shaft(s). Can anyone shed some light on other potential causes for these error codes and associated fixes?