Useful information to include:

• 1.16.5
• 1.91.2
• I put a diamond pickaxe in a crafting bench with a normal turtle and it wouldn't craft into a mining turtle.

I think I have a similar issue: if you have a pickaxe that has any nbt data on it (say, you have origins classes and went miner, then made a diamond pickaxe) the turtle is then incapable of equiping it