Making a test run of the interface validator for all existing interfaces in Netbox I've found that some interfaces in the mr1 devices don't have the MTU set. As agreed with Arzhel opening a task low prio to set them when feasible.
This is the list of the ones reported right now:
mr1-codfw (WMF5617) ge-0/0/0 - {'mtu': ['Invalid MTU None, must be 9192']}
mr1-drmrs (WMF10165) ge-0/0/1 - {'mtu': ['Invalid MTU None, must be 9192']}
mr1-drmrs (WMF10165) ge-0/0/2 - {'mtu': ['Invalid MTU None, must be 9192']}
mr1-eqiad (WMF4931) ge-0/0/0 - {'mtu': ['Invalid MTU None, must be 9192']}
mr1-eqsin (WMF7247) ge-0/0/1 - {'mtu': ['Invalid MTU None, must be 9192']}
mr1-eqsin (WMF7247) ge-0/0/2 - {'mtu': ['Invalid MTU None, must be 9192']}
mr1-esams (WMF11826) ge-0/0/3 - {'mtu': ['Invalid MTU None, must be 9192']}
mr1-esams (WMF11826) ge-0/0/4 - {'mtu': ['Invalid MTU None, must be 9192']}
mr1-ulsfo (WMF7259) ge-0/0/1 - {'mtu': ['Invalid MTU None, must be 9192']}
mr1-ulsfo (WMF7259) ge-0/0/2 - {'mtu': ['Invalid MTU None, must be 9192']}
mr1-ulsfo (WMF7259) ge-0/0/3 - {'mtu': ['Invalid MTU None, must be 9192']}