After 2 years of use have just discovered TM is only backing up 50% of my files. Have searched Web and it seems this is a common problem. Emailed Tim Cook about it but no reply!. Really this is touted as the best way to protect your Mac and here it is failing stupendously. I have 3T backup drive and 2T of files. I found one folder that should have had 14 subfolders with only 1 backed up. Anyone have similar experience?