Do you quarantine snails (e.g. Nerite, MTS, ramshorn)? If so, do you treat the water with salt or any other form of medication? Or, do you simply place them in their own tank and just keep an eye on them for 2-3 weeks?
I have not but have always gotten snails from either local hobbyists or from a vendor that quarantined the nerite snails she used to sell. It wouldn't hurt to quarantine new snails for a few weeks and monitor both their eating and behavior before adding to your main tank. I'm not familiar with medicating snails so can't help there.