Contacts Names or Addresses Not Showing Up When Typing In Outlook Client/OWA

We have a client that having a specific wierd issue we can't seem to recreate and yet it happening to him both in Outlook 2013 and Outlook Web Access.

When the user is adding a address that in his CONTACTS/ADDRESS BOOK or in his autocomplete cache, the name or email address doesn't show up (autopopulate).

These contacts the user is sending to are people that he frequently emailed back and forth.

Normally when you type in a name or email address in the TO field, it starts to autofill the rest by pulling from the last time you emailed the person or from the user's contacts list if he in there. However this user said it doesn't happened sometimes. What he does is he have to search his sent items or TO items from old emails he received and copy the email address and then paste the email address into a new email in order to send it. Afterwards, that same email will start to autofill when he types it in but it seems to be happening randomly where this stops working and i can't find any evidence why this might be happening or seen it myself.

Any ideas or have anyone seen this before?

Office been reinstalled (uninstalled, then reinstalled, not repaired)

Profile been recreated. Doesn't seem to matter.

I checked the .dat roaming cache file but deleting that and having outlook recreate it doesn't seem to do anything. I also use a nk2 browser to view the DAT file and I see all the autofill contacts in the email.

Right now we have to empty his autocomplete cache in Outlook, and then repopulate it with his address book at least once a month but it is a band aid fix

I thought it was just happening to the user's outlook but he also saying it happening when he using Outlook Web Access so don't think it has anything to do with the local autocomplete .DAT file/cache file.

The user showed me in OWA, when he types in a address book user, it doesn't show up as a suggested contact unless he clicks on "search contacts and directory" in OWA. He doesn't want to use the search contacts button, he wants to just be able to type in and outlook gives him suggested contacts like it does in Outlook desktop app. I can't seem to find a way to repopulate that part in OWA since I can only do one email at a time. Even then, he said sometimes it doesn't work at all where he sends a email to a user he sent in the past and then some time later, it doesn't work again, having to re-add it back to the suggested in OWA by doing the search contacts again.