You think it might be that.
Mine is at 99.9% for some time now too.
It did work after the install.
I think it is broken.
I am reading posts the dht22 sensor is of a very poor quality.
Some people have replaced the sensor 2 to 3 times already.
They like to install the bme280 sensor also, just like you.
The SHT31 sensor seems to be of a better quality but isn’t supported by luftdaten.
Just reading this stuff, I have no experience.
I have 2 new dht22 sensors lying here.
I will replace the sensor soon and see if it’s actually broken.