You have created a PDF Form Recognition archive document as a reference, but when testing DLP recognition capabilities you are getting inconsistent results
15.x, 16.x
On premise detection servers (NPW, NPE, ND, NM) not endpoint
There are multiple possible reasons that a PDF reference-document may be unreliably detected in DLP:
For detailed information see this Help Center topic: Preparing a Form Recognition Gallery Archive (broadcom.com).