I am experiencing the same issue with related records functionality in WAB 2.8. It is showing the related tabs with no data.
In the _resourceManager.js 'getRelationTable function is getting the layerInfoId from the shipInfo.id property.
var layerInfoId = lang.getObject('shipInfo.id', false, currentShip);
and its giving "no activeLayerInfo!" error in _getQueryTableInfo function because the tabId is undefined.
Thank you!