Unable to get property 'ADDITION' of undefined or null reference

[poloka]

Having some difficulties in determining what would cause the MutationEvent object to be undefined. Error thrown on the following line:

var oldValue = e.attrChange === MutationEvent.ADDITION ? null : e.prevValue;

Currently running IE 11.0.32 build 11.0.9600.18349CO (KB3160005). The site I am debugging has no access to debug so flying blind. Works without issues locally and in another remote site utilizing a 11.0.4x build of IE. Wanted to get your thoughts.

[poloka]

Maybe to add a bit more context, this is packed as a dependency within XFC

[poloka]

#8