How to clean tannic acid stains on the terrace?

Good day.
We are currently working on our terrace roof. To protect the paving from possible discoloration caused by the painted beams, I placed a few wooden slats underneath them so that they do not rest directly on it.

Now the positive: the paint did not leave any stains. The negative: one of the slats was made of oak wood and after the rain it left an unpleasant streak on the paving. I couldn't explain it at first and started googling... and behold: the wood reacts with the alkaline concrete paving and tannic acid seeps out, leaving a mark similar to rust... is there any way to clean this? Has anyone had experience with this...? Otherwise I will probably have to replace about 25 stones...

We also had this on our beige pavement. Our child received an oak sandbox as a gift shortly after moving in, which we first placed on the terrace before choosing a permanent spot and digging the pit. The rain then spread the tannic acid in a nice square shape on the pavement. The good news is it goes away again. The bad news is it takes some time. Scrubbing and water made it a bit better but it was still clearly visible. I don’t even know if, in the meantime, we used chemicals on it. What helped, however, was time, sun, and rain.

I see it the same way as my predecessor. I am also not sure whether you can get rid of the stain with chemicals or other agents. In my experience, however, the course of events (namely time, weather, and other influences) naturally reduces such stains on its own.

I have now bought a mold remover for about 12 euros from a large online retailer, which also advertises the cleaning of tannin stains... the reviews were very promising.

However, I could not test it because the stains had already significantly receded within almost 2 weeks... so I refrained from using it for the time being...