For those who do not want to read into trouble and try whether they have this bug or not I've made a video:
https://www.youtube.com/watch?v=y4DQwzDfudI
https://www.youtube.com/watch?v=y4DQwzDfudI
yap, me 2 , i think everyone got this bug .
Finally someone explained it correctly. The link bonus keeps working, the slot itself doesn't, so you end up with weird values.
I've no idea if "everyone" gets this (it's the rare bug that has 100% of ppl reporting they have it), but since even the most detailed explanations up until a post or two ago were flat wrong I'm not surprised there's misunderstanding. Regardless, it ought to be fixed. So sick of reslotting mutagens every time I load a game/fast travel/die.
The effect of the bug is fairly minor, though real.
If we have a 300 attack sword (typical mid game silver, mid-late steel):
A single Greater Red increases damage by 10%. It is boosted by 10% for each Red skill attached.
This means that the effective strength without the bug (and with no skills/bonuses applied) is 420, with the bug it is 390. Other bonuses are applied against the base value, not this modified one, so the other attack skills (e.g. Cat and Precision) give 45% increase or +135 ~ for 435 damage without any mutagen bonus.
Total basic damage with one mutagen and these skills is then 525 with the bug, 555 without (just over 5% deficit). With 3 mutagens it gives, 705 with, 795 without the bug.(Just over 11% lost).
The total is used for critical damage though so the lost damage in basic attacks does continue to be lost in critical ones too. I've always found it worthwhile to re-apply the mutagens on starting a game session (and take the opportunity as a reminder to check active skillset and equipment condition (which can otherwise be overlooked for a long time (note that equipment condition and performance is lost before the red condition is applied for player notification)). Not doing so isn't transformative for gameplay though. Oils, weapon enhancement from grind wheels, condition maintenance and runes can more than compensate for the lost basic damage (though could be used to enhance the full value if the loss isn't experienced).
Not as sure how important the effect is for signs and alchemy...
...the mutagen "stash" is literally the worst thing ever in a video game. How did that leave the studio
...for me it's not like that