To get rid of too much glimmer, I would make sure every weapon in my vault was at least masterwork Tier 3. That was the case at the end of S11. Just recently today, I noticed a great many of those same weapons were reduced by 1 or 2 masterwork tiers. I think it might have been a fairly recent bug within the last week or two, as I'm sure everything was fine during the first few weeks of S12 Beyond Light. It looks like it's just happening to weapons that were sunset. Either way, that's a pretty crazy bug, representing a lot of invested resources lost.