If you have a custom lookup field on the Campaign Member, adding that field to the "Campaign History" related list on a contact or lead page layout breaks the related list in lightning (see http://salesforce.stackexchange.com/questions/163049/invalid-field-error-when-adding-a-custom-lookup-field-onto-the-campaign-history).

I've been told through Salesforce Support that it's related to this issue that deals with the package.xml for Campaign History - https://success.salesforce.com/issues_view?id=a1p3A000000E1MCQA0

What's the best way for this issue to get the attention it deserves? This is impacting some of our clients and is easily reproducible. The related list works fine in Salesforce Classic, but is broken in lightning. In my opinion, a broken related list is higher priority than a missing field in the package.xml as it's a user-facing bug...