Okay, so, the last few weeks I have been facing the same issue to where I start to lose my materials when I enter the tower. I check the post master and they are not there, I close the game and come back, they are still not there. I realized this when I went into collections to claim and exotic and it was saying I had no gunsmith materials when I just dismantled a lot of armor and weapons. I looked to see if I really didn't have any and long behold all my mats were gone and any time I would collect them it wouldn't even show up in my inventory. After opening a few season level ups with material collection boxes (idk the actual reward name) It still wouldn't give me any mats. This keeps happening on and off and its so frustrating because I always run into an issue not having the materials I need to progress.