Bulk edit of products in MarketPress sets prices to zero

MarketPress 3.1.2, WordPress 4.7
If I bulk edit products in MarketPress all prices are set to 0 - even if I empty the field (which defaults to 0 at the input field).
1. Products with prices selected to bulk edit

2. Bulk editing (adding the product tag "special":wink: and removing the 0 from the price field

3. Resulting overview of the same products: All prices are set to 0

Please advice, thank you.