This list i made while completing a game several month ago. Sorry if you already know them but i have very limited internet access and don't have much time to search forum to see which bugs are already known.
Game Version - 1.04
In Alchemy window you can put any item in Reactant/Reagent slot if you put it instead of correct Reactant/Reagent.
Enchanted 'Demon Oil' ('Demon Oil II +3' or similar) don't act like it should: there is no ignition on impact and when you hold 'shift' key there is no lighted area around cursor that shows where fire will be.
When hero is under 'Haste' spell, you can make several moves (instead of normal two) per opponents turn:
1) do first action in your turn
2) save game
3) do last action in your turn (so opponet take his)
4) load game you saved (by that point you supposed to have one action left in your turn)
5) you do your action and opponent don't take his turn!
6) you still have one action left in your turn (or you can repeat that trick)
Though you limited by duration of the spell.
When 'Mana Fortified' effect is active casting cost of spells isn't reduced by half resulting you can't cast spell you need, though you have enough mana points to cast them (counting effect).
When monster poisoned by 'Poison Spray' dies hero gain no experience for that.
Map Holes (hero can get to black area through these squares):
1) 'Whistling Cave' (X=62 Y=122)
2) 'Blackwater Region' (X=82 Y=35) (X=93 Y=35)
If hero walk on a (X=1 Y=59) square in 'Northeast Crakamir' it will be trapped in mountains in 'Northern Crakamir'
'Portal' spell issues:
1) Actual casting cost of this spell is 6 mana points per casting level, not 10.
2) There is no check for available mana points for 'Portal' spell (set anchor or open portal). Mana points can even go beyond zero (and you still be able to cast this spell).
3) In Spell Journal 'Portal' anchor points shows when you choose 'Lock Melt' spell and hover mouse over casting level signs. And they shows next to different spells, depending what spells you have in journal.
a) (Bless, Cat's Eyes, Detox, Heal, Entangle, Fleshboil, Leatherskin, Lore, Poison Spray, Nimbleness, Ogre Strength, Charm, Cure Disease, Ench. Weap., Haste, Sunder Flesh, Stoneskin, Turn Undead, Smite; D. Lights, Air Shield, Fire Dart, Gr. Flame, El. Armor, Reveal Map, Pr. Sight, Sonic Blast, Comp. Atm., Enk. Weap., D. Freeze, Fireball, Chameleon, Lock Melt, Trapkill, Portal, Inviibility) - near 'Portal'
b) (all in 'a' + 'Supernova') - near 'Portal' too
c) (all in 'a' + 'Mass Boil' or 'Dehex') - near 'Trapkill'
d) (all in 'a' + 'Mass Boil' and 'Dehex') - near 'Lock Melt'
And when you choose 'Portal' itself anchor points don't shows at all.
Shadowmirk wizard.'Erubor' or 'Erudor'?
1) Brother of the main hero (in Vela) once says 'Erudor' instead of 'Erubor'
2) When hero start speaking with Erubor: "Erudor paces around his study, ..."
Blackwater tavern. If you talk with 'shadowy individual' and then kill him you get message that you can't complete a quest anymore, but all quest entries remain in Quest Journal.