In a statement emailed to customers, Limited Run says those two games weren’t manufactured by its “regular” manufacturing partner. “Due to an issue with voltage regulation, there is a small chance that prolonged use of these titles could result in damage to either the cartridge or the console hardware,” Limited Run says.

The company is stopping further shipments of the games to customers so that it can re-manufacture them itself “via our trusted manufacturing partner,” according to the statement. Anyone who has already received the games will be sent “a newly manufactured version of their title automatically,” Limited Run says. The company does not recommend using the older version of the games.

Customers can ask for a refund if they want by contacting customer service. The two games currently aren’t for sale.

Limited Run says the manufacturer that produced Rugrats and Piopow “has only worked on a very small handful” of Limited Run titles, and the company is “going through our back catalogue of NES titles manufactured by this supplier and testing for possible issues.”