Syndicate Medallion riven mission not progressing

[World]

Hi, so im trying to unlock a shotgun riven which requires me to collect a number of syndicate medallions. However ive now collected around 15 an the riven isn't progressing at all.

I just want to clarify - Yes I have the mod equipt, and yes im bringing the weapon along to the mission. It even gives me the riven challenge prompt as I initially load into the mission. I've had this issue in the past where ive just had to sell the riven as it became impossible to complete even though ive met all the conditions.

Mission Results:

Riven progress after this mission:

Edited July 13, 2019 by footlongturkey

[actionbilly]

I got 2 rivens with the same problem. I bought them both they might be bugged and sold to me because the precvious owner didn´t know what to do either.