Error 484 out of nowhere

Hi all, can anyone give me some insight on Error 484 (address incomplete) displayed on the phones (GXP2000 Grandstream) This started occuring out of no where and persisted after reboots of the phones and the PBX and after restoring for a earlier config - nothing has changed anywhere?

The error occurs when a user tries to dial an outside line right after you hit the 9 key to get an outside line?

-If the user dials 9 and then the rest of the number VERY quickly - all is well
-if the user dials 9 and pauses for about a second, then they get the error