I found two regression in the MediaInfo support in WikibaseIntegrator:

During the splut between BaseEntity and MediaInfoEntity, some code migrated from one file to the other one, but was commented:
I think it's a mistake from my side:
af30069#diff-5506aaa6621db95681c0f1df605ad3eaed7de64934b5f038ebec3ba19fb7cbe0
This changes broke the "write" part of the MediaInfo support.

The other one mistake from me, was when adding support for the "props" field, allowing to support optional fields when getting entities, to speed up the process, and the reducing the bandwidth used:
85e8515#diff-5506aaa6621db95681c0f1df605ad3eaed7de64934b5f038ebec3ba19fb7cbe0
The issue is located line 146 of the mediainfo.py, where I check for the aliases field instead of the statements field.
This changes broke the "read" part of the MediaInfo support.