Hello,
There Modok in Variant 3.1 which is stun immune, here are his nodes:
Modok
isn't a TECH champion, He is
SCIENCE champion. He is has robot tag, but nodes says: "All
TECH Champions in this fight are immune to Ablility Accuracy Modification"

I brought 4* Black Widow at sig 99. Here is her ability:
This means she has 70 + 15% = 85% abilities reductionI brought Quake to the team:

This means BW now should have 85 + 15 = 100% abilities reduction while hitting. Unfortunately, this is not the case.
Let's say 15% sinrgey is from the current percentage.
15% of 85 is 12.72, then: 85 + 12.72 = 97.75%!!!
I did this fight with her 3 times and all the times I got the same result:'
https://youtu.be/Gly08Xhgm-wDevice: iPhone XS (doesn't matter tho)
Area: Variant 3.1 (White Magento quest)