Expected Result:

When repaired in a Crafting Interface, Custom Tool maintains any Component Data except Enchantments, Custom Name, etc.

Actual Result:

It loses all Component Data except Damage and Max Damage

Steps to reproduce:

1.  Give yourself the Custom Tool two times using the following: 

   /give @s paper[minecraft:tool={rules:[{blocks:"#mineable/pickaxe",correct_for_drops:true}]},minecraft:max_damage=100,minecraft:damage=0,minecraft:max_stack_size=1] 2

   Maybe also check the Data using the following: 

   /data get entity @s Inventory[<index of tool item>]

1. Mine something that you would mine with a pickaxe and see the block drop
2. Repair the tool in a Crafting Interface using the duplicate one
3. Try mining something again, notice it won't drop anything.
4. Check the Data again: 

   /data get entity @s Inventory[{id:"minecraft:paper"}]

1. See it lost Data that it probably shouldn't have (Tool Data, Max Stack Size)