The difficulty here is that this is a mod issue. You cannot plant mushrooms or cloudberries in Vahleim (vanilla). So this "snap" feature is either a feature of the mod or a bug caused by the mod because, again, not something Valheim does.

Has the mod been updated to work with the current version of Valheim? Mods are notorious for "breaking" when game updates come out.

You might have a better chance of finding a solution by asking on the discussion pages for whichever mods you are using.

Just a guess ... but whichever mod is causing this issue may be causing your construction issue as well.