We use Aptamil and it is the same for us. It is important to clean the powder container and the funnel regularly with a mild detergent. We clean the funnel every time with detergent and the powder container weekly. We have noticed that fewer chunks fall out this way. It is also helpful to fill up the powder every time it reaches the min. and max. levels so that the powder has less contact with the air.

It happens from time to time that there are larger lumps.
My experience is that if the "funnels" are not 100% dry after cleaning, then there is a significantly stronger lump formation.
But it's not a problem, just give the shop a good shake a few times and then it's fine.

It was with us too, but dissolved again in the water.

Yes, it was the same for us over time - the same powder. We had the feeling that the surface of the funnel was no longer as good.