invisible enemy Boar

In the first ruin you go to get aloth, the first encounter you get (i play on POTD difficulty)  the Boars you have to fight are invisible in my game but only the big one .

If i pressed tab i can see their names label over their invisible models and when i stealth and pressed tab i see their vision cone too, and they seem to appear only when i engaged them or they engaged me

Anyone have encounter this bug? can it be fixed will I encounter more invisible enemy along the road ? im on pc btw gog version

EDIT: This is cause by Galawain challenges I had a hard time to find info on this so i gonna paste it here in case someone else think its a bug also

Galawain: all beasts in the game gain one of ten random permanent buffs, determined at the start of the game (so you can't save/reload an area if you don't like what you get). How it works mechanically is that beasts are grouped up into "batches" per an encounter or area, and an identical buff is generated for the entire batch in one go; this can result in an entire area of beasts with the same buff if they were all designed as the same "batch." This can make certain buffs more punishing than others depending on how big the batches are; Volatile or Bullish is not bad on a single lone beast, but on an army of spiders or wurms can be brutal. Anyway, the ten buffs are:

• Vampiric: beast converts damage they do into health (I believe 15%).
• Reflecting: a portion of damage a beast recieves is done back to the attacker. (I don't know the exact number, possibly also 15%.)
• Unstoppable: cannot be interrupted or affected with afflictions (other debuffs and manual flanking still work).
• Exalted: permanently gain a random tier three inspiration. Permanent really means permanent. You can't counter it by applying a matching affliction. Nor can you suppress it with Arcane Suppression. (Though I have had an encounter or two where the inspiration has buggily gone away somehow.) Note that Brilliant is not that bad relative to other inspirations because most beasts already have infinite uses of their abilities that are only constrained by AI scripting so the resource generation effect of Brilliant effectively does nothing.
• Vengeful: every time an ally dies they gain a stacking +1 PL buff also called "Vengeful." Note that as far as I can tell, beast basic attacks don't get any PL scaling, so on a good number of beasts the stacking vengeful buff might have at most minimal effect.
• Accelerated: attack action speed bonus.
• Bullish: all attacks interrupt and push back on hit.
• Hardened: much higher AR and health.
• Prowling: at the start of an encounter and every time this beast kills something they go invisible until they attack.
• Volatile: upon death a fireball is launched at their corpse and does significant damage.

Edited February 7, 20205 yr by truths33ker
I have found the reason of this issue