Massive moisture in the walls timber frame construction in summer

Good day, last year we detected mold infestation on the interior walls of our timber frame house completed in 2012. Several experts were on site who considered the window construction to be the cause. It was found that the entire base was completely filled with water all around and that the water had risen into the stud area and soaked the entire structure. This was followed by an almost year-long renovation. I then purchased a moisture meter with electrodes, with which I have been regularly measuring and keeping a record since the completion of the renovation to check if moisture reoccurs. Everything was fine (about 13 - 15% moisture) in autumn and winter. However, since it has become warm, the moisture in the wall area/inner base area has risen enormously again to 20-40%. My construction company blames the damp summer months, but I do not trust this and suspect that the walls or the floor slab are now producing a lot of condensation in the summer, even though the wall structure with OSB panels is designed to be vapor-permeable. I can exclude a leakage in the water pipes because a specialist company was here and tested this by pressure testing. I also consider water ingress from outside to be very unlikely since the moisture did not rise during the cold months with a lot of rain. I am somewhat desperate because I fear that the entire renovation and search for the cause will start all over again, and this time it will hit me financially hard since the warranty is about to expire.

Are these moisture values really normal in the warm months?

Hi. What did you come up with?

Hello,
multi-layer constructions, all timber frame houses are risk constructions from the outset. Once water enters the construction, then the deconstruction follows, as happened in your case.
After the renovation, everything was dry!
Where do you measure, in the wall area (in the insulation) or on the surface?

Regards, Christoph