Andy, can you check if items can disappear? My theory is as follows:
Get +1 inventory for uncommon towers, so they have 5 space, but rares and unique only 4.
Build an uncommon or common, for example, jilly. Equip het with items. Replace her with unique tower, for example dark forge.
I think in my current game I lost an item when I transformed a tower to another with less space.
same issue another circumstances.
>equiping viking helmet
>using potions (through ygg+rings combo. ygg aktivates potions)
>disequiping viking helmet
>> roordahuizum disapeares.
not beeing in mulis nor the general itemstash.
i hope the description helps.