Currently if you dont have Braytech MK 2 Scout (i have a Catalysted Polaris Lance but when Bungie bugged the MK 2 and then fixed it mine never returned to collections meaning i have to get it again. :/) then it is unobtainable due to the quest step requiring Psionic Potential being bugged.
You might be wondering why that matters if you dont really need Polaris lance? Well Braytech MK 2 is required for the Badge for Curse of Osiris/ Warmind Destinations which is necessary for Wayfarer Seal. So essentially not only does this keep people who dont have Polaris from getting it they also cant get Wayfarer seal which potentially locks out an achievement/ trophy.
Hopefully Bungie will look into this. i have a link to the video proof i took after it happened 4 times in a row.
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Try doing all the other adventures first, and then try to do the original one.