I am not sure exactly what is not right in your case, but I have checked the spots that Rob's scraper takes from wsprnet.org for the last ten days and there are many examples of transmit callsigns with prefixes and suffixes. For example:
DF4PV/M, DJ2WW/P, EA8/OK2SAM, G0SZI/A, GM4SJB/2, HR9/WA4DT, MM/M0VIK, SM7PNV/2, TA4/G8SCU, W5/VK2ARH, W6LVP/V, W7GDK/7, ZS3D/N
including, I see, your own call as SM7PNV/2.
In your email you wrote "SM7PNV/p", was the lower case p a typo?
Your example "OZ1/SM7PNV" is exactly the same character count and distribution either side of the / as EA8/OK2SAM which is in the database.
So, I do not think there is a general problem, but I cannot see what you are missing in generating your own Type 2 messages. Sorry.