I think the paint actually isn’t dry. It could be that the ground lair(s) weren’t totally dry/hard before the regular was put, or the regular has not been properly stirred before applying, thus the siccative/drying agent wasn’t well mixed although I am not totally sure if that is true or a myth, or the location of the paint job was too cold (under a certain temperature we were not allowed to paint I think it was 5 Celsius). Three weeks is already pretty long, but it happens sometimes that certain paints take ‘forever’ to get totally dry, and hard. This is all knowledge that I gained from hear-say, so it could be that other Jellies have more accurate explanations.