Self Service Procurement App (25A) does not support Secondary UoM

Summary:

I am in the process of implementing the new SSP Responsive App (25A). Upon testing, there is an error message thrown on ALL inernally stocked items:

Error: You can't request an internal material transfer for dual UOM-controlled items. (POR-2011144)

I tried to search this error but couldn't find any response. Is anyone able to shed some light on what it means and how to rectify it?

Content (please ensure you mask any confidential information):

All our items usually have a Primary UoM e.g. Box and a Secondary UoM e.g. Each. to seperate from purchasing vs issuing as per standard practice. We do not have Dual UoM enabled.