Contact sync problem

I have a problem of syncing contacts from outlook-desktop to outlook.com to windows phone 8(on Nokia Lumia 720). I have followed all instructions on Microsoft site, used hotmail connector to connect my outlook.com account and configured Nokia Lumia 720 with the outlook account which works. However the contact sync appears to be unreliable. My address books on each of the 3 locations differ by about 10 to 15%. I add new contacts on either outlook on desktop or on phone, depending on where i am when i get a new contact. I observe that the sync happens for some contacts and simply does not occur for some others. I have posted this several times on microsoft and nokia forums, but apart from people pointing out to the relevant microsoft material (which i have read and followed), i have not got any response which solved the problem. The only reliable way i have found so far is the dumb way of emailing a vcf card to myself when i create a new contacts (so that i can save it on the other side). For a business user, contact sync is a very important basic need. Hope you can help.