Just so I don't leave this hanging... The Network Engineers finally figured out what happened. Originally they thought the changes they made would not cause our problems even though it occurred at the same time their changes went live... hmmm

Here is their final findings:
What we learned: If a Cisco IOS router is configured with mtu x and is connected to a Cisco IOS XR router, then the corresponding interface on the Cisco IOS XR router should be configured with mtu x+14 for Ethernet
interfaces, or mtu x+4 for serial interfaces.

Cisco IOS and Cisco IOS XR software have the same meaning for the ipv4 mtu, ipv6 mtu and mpls mtu commands; they must be configured with the same values. You can use the command mtu 1514 or ipv4 mtu 1500.