Almost forgot, but there was an issue which could be related:

• https://hibernate.atlassian.net/browse/HHH-12384

Could you try setting the system property hibernate.bytecode.enforce_legacy_proxy_classnames=true ?

N.B. this has to be a system property, it can not be set as an Hibernate configuration property. Also, it should no longer be needed if you have a Spring updated enough to include https://jira.spring.io/browse/DATAJPA-1347