例外原则\ORM\映射\MappingException'和消息'目标实体X不能在Y中找到

I've been getting the above error whenever I try to use EntityManager to find or query for an object with an association. I absolutely cannot find any rhyme or reason for why a target entity cannot be found. Below is some sample code and error. I haven't redacted the specific names, because this might be a namespacing issue.I've been getting the above error whenever I tr