Bubbles on sensor? BMPCC 4K

Hello, started editing video and discovering lots of artifacts on shoots, checked sensor and found these dots on it, thought it was dust or dirt, but it is impossible to remove it, it looks like bubbles under film protector. Thing is I have never removed the lens, lens is ok. Does anyone have the same issue?

What are the climatic conditions where you live?

Spain, not far from Barcelona, I use this cam for about 4 years in same conditions, this issue become about month before.

I was assuming some kind of fungus. But it might be simply chemical degradation.

I tried extreme measuring, cleaned the sensor with acetone paint thinner, but there was no result, so it was not dust or fungi. Looks like matrix screen damage somehow, but have no idea how this happened. I have only one lens that I never change and stay fix with body all the time...
photo with difference between 2.8f and 20f