devtrackers.gg
This isn't a bug, the level rewards exotics on the first play of the week but if you look at the mission on subsequent times it does not guarantee gear it guarantees resources. I invite you to feedback on that but that is intended at the moment. Just wanted to clarify expectation. When you play high level content keep an eye on loot advertisement, they often have a far better reward pool for the first play every week.
*Edit* I just want to stress that i said subsequent play does not guarantee gear, i did not say you will never get some. Just to be very clear on that point.