A player has a golden Goldrinn with reborn and two golden Bananas. The Goldrinn dies first. With its new +6/+6 deathrattle and baseline stats of 6/6, it should be reborn as a
6/1+6/6 = 12/7
Which is then mutiplied by 3 twice because of the bananas.
12/7 * 3 * 3 = 108/63
It can, however, be seen in the video that it is a 132/87. I have reasoned that this happens because the +6/+6 aura triggers after every stat increase, so that
This is once again the consequence of an aura effect (not saying it is normal)
Just like you conclude, the deathrattle buff reapplies after each banana effect
Because each banana effect does not give stats, it sets them. And auras apply themselves over stats set effects.
If you have a beast summoned as a 5/5, and let’s say a mama bear gives it +5/+5.
Your beast have set stats of 5/5 at the start, and the buff sets their stats to 10/10.
On top of that, the aura of Goldrinn applies and your beast is now 13/13.
But its set stats remain at 10/10.
What banana slama does is check the total stats of 13/13, double (or triple) it, then apply that maximum as a new stats set effect (just like Uther sets stats to 15/15).
So it sets the stats to 26/26. But then, the aura reapplies itself on top of that effect and the minion becomes 29/29 after its stats being “doubled”
What banana slama should do is check the total stats, and give that amount, or the double as a buff. The minion would then have 10/10+13/13=23/23 of “set” stats, plus the 3/3 of the aura making it a 26/26, having its stats accuratly doubled
This is an assumption of how it appears to work that may help to understand the behavior (once again not saying it is a normal behavior)
Auras and stats set effects always produced these behaviors but they really introduced a lot of both in the latest updates of the game