The filter logic for the loadouts is incorrectly treating unavailable rarity levels the same as if they were filtered out. Say you don’t have any Lead loadouts in your inventory and decide to filter out the Default loadouts, from now on both Default and Lead will be filtered out (along with any other rarity level you did not have at the time). Whenever you change your filter, level that are not currently in the filter list should retain their previous filtered / visible status. It’s even more silly when the change you do is to “Clear filters” or “Show all”: you would expect all levels to now be visible, but in fact any level not in the list at the time will still be filtered out.
This is most obvious when viewing loadouts by merc under Barracks > Mercs > Full Profile and swapping mercs with the radio buttons at the bottom of the page (the filter list wasn’t touched between these pictures except to pop it open).
Starting with Arty, notice how the “Clear filters” button is not there, indicating no active filters:
Selecting Aura next, the Cobalt level is checked off in the filter, a setting inherited from Arty for whom I don’t have a Cobalt loadout:
Fragger next, Silver and Obsidian are now checked off since Aura didn’t have any of those. Special Edition is still visible since both Arty and Aura had at least one of those:
Stoker next, now down to Default (no rarity) only, since he doesn’t have any SE, the only other rarity left after going through Fragger:
After that, any merc you select will only show its Default loadout:
Clearly rarity levels visibility should not be toggled off just because you look at a group of loadouts that doesn’t contain any of that level, filter persistence should be independent from the tailoring of the filter list based on availability.