Yes, I know. However, there are two reasons for being on Docker (and I also remember your post here @rlkoshak, which was spot on). First, I did not get wmbusmeters running in the first place on openHABian when I started with openHAB two years back (but it could’ve also been my mistake), and got it running immediately with the wmbusmeters docker image, and second, well, what shall I say, this entire “Docker/Portainer thing” is just my guilty pleasure as I wanted to learn some new piece of tech, …, and now I’m paying the price with a high RAM load and the need to buy new Hardware because of that. 
Good question. II assume I did a pretty standard docker install. Any idea how I can check why this is the case? Besides the strange entries in htop, I do not experience any other problem.