After Kear Morhen battle i realized much too late a Dimetrium Bomb bug on PC 4.02 In that battle you can pickup dimetrium bomb loot if you run out of this bomb, as i did. After its over i just wondered why i have only 2 dimetrium bombs not 4 as all others, TILL THE END of the game i didnt look why. After the epic final battle, where i badly needed dimetrium bombs against WildHunt bosses i realized my "superior dimetrium bomb" before battle of Kear Morhen turned into a "normal bomb", then i could do alchemy bomb upgrade back to superior. so CHECK your dimetrium bombs after that fight and before the Endgame.. could be you pick up Vesemirs "normal bombs" which then dont switch back you your already crafted superior bombs..