Blackstone and Cobblestone

Hello! I am here at Saturday, October 3rd, 2020. I would like to report a bug that is very odd. Sometimes when i'm playing survival mode, I go to craft something made of cobblestone like a tool or a furnace. for an example, I click on my crafting table to go make a new stone shovel because my previous one just broke. I go to the search section and search shovel. All the different types of shovels pop up like normal. I click on the stone shovel and instead of cobblestone, Its blackstone to make the shovel. If you don't understand what I mean there is a stick at the bottom, stick in the middle, and blackstone at the top. Sometimes it works normally and sometimes it uses blackstone instead of cobblestone. I am playing on mobile and I don't know if it works normally on different devices. Thank you for your time and please fix this soon!
Sincerely,
Madeline Luckock