Based on what you've described, it sounds like the most likely scenario is that your trouble may be related to updating specific contacts or contacts that have duplicates in your account. Is it possible to recreate any of this behavior if you create a new contact and then try to update it?
If the behavior is not happening with new contacts, then it's likely that we need to look more closely at the specific contacts that you've been working on. I that is the case, then it would be best to collect up some information (such as the email addresses and contact IDs that are having issues) and email that to us at email@example.com.
Please let me know if you have any questions!
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