This is the issue with the Casanovum tests, like with your clear & simple here, the dye can be like this and it takes longer than the One Step tests I have used to clear. They do eventually but some are more streaky than others which can make them difficult to read unless it's blatantly obvious.
I don't think you will find any ICs with squeaky clean reviews, they all seem to have their own unique cons between them!
I order One Step blue handle tests from Amazon, I know after having so many lines which weren't lines to expect this to happen, and I think you have to make your peace with their faults and only pay attention to them if you can see a clear line progression after a few days