Bug: Hazoret's Undying Fury interaction with Goblin Dark-Dwellers

Chaostheory

I couldn't find a post with this, or a mention in the bug list, so here is the bug and potential fix to it:

Cards:
Hazoret's Undying Fury: Spell, Fetches next 4 spells and sets their mana cost to 0, can be cast on same turn.
Goblin Dark-Dwellers: Creature, Fetches last spell that was cast from graveyard. Gives it 6 mana.

Issue:
If I cast Hazoret's Undying Fury (fetches 4 spells and sets their mana to 0) followed by Goblin Dark-Dwellers (fetches last spell from graveyard and gives it 6 mana), I will get the last cast with Hazoret's Undying Fury to my hand, but with 0 mana instead of 6.

Potential reasoning:
I believe this because:
1) Hazoret's Undying sets mana cost of the spell to 0
2) The spell retains the mana cost of 0 in graveyard.
3) Since a card cannot get more mana than its maximum mana cost in MTG: Puzzle Quest, the mana will never get added to the card once it is brought back to hand.

Possible Fixes:
Simple fix would be to apply a check of state to cards once they enter the graveyard, which would probably fix some other issues as well. Another way would be to reset the mana cost to initial state before giving the mana.

I was able to reproduce this bug if the Goblin Dark-Dwellers was cast on same or different turn than Hazoret's Undying Fury.

I cannot see how this would be intentional and not a bug. The bug also prevents potential combos with Evolving Wilds and similar.