The size limits in Sonarr are greatly flawed. In a perfect world you should be able to adjust the minimum and maximum sizes independently, which would solve this problem, instead they move on a sliding scale.
You're better off doing away with size limits entirely and just relying on quality profiles.
Just untick webrip from the profile that is assigned to that show and it won't download web rips, if some episodes don't meet the criteria of web-dl then you'll just have to do a manual search on the episode. Thats what I do. If you want quality to be consistent you will unfortunately have to put in the work and manual search for episodes sometimes.
Its the only way at the moment to make sure you don't get 5GB files.