Organizations vocabulary is partially bugged
The organizations vocabulary is apparently too big to query at once (~60MB). No paging is offered by the Coscine REST API afaik. Handling this vocabulary properly and allowing users to set/edit organizations in the ProjectForm apart from the first 100 entries probably needs some more work. Either via filter arguments at the generator stage (and consequently making the field uncontrolled) or by implementing some special if case in set_value() of ProjectForm for the organizations field.
For now editing projects works, but only if not touching the organizations field. Also existing organization metadata might be altered (if an RWTH organization has been set, but it's not found in the vocabulary, it is cut off and converted to RWTH Aachen itself, not the original institute). Therefore caution must be taken when using the ProjectForm at the moment.