Targeted task:
A blank shield, that is enchanted with Mending and/or Unbreaking shall be decorated with an Illager Banner.

To that end the shield and the banner get put in the 2x2 or 3x3 crafting grid.

Observed behaviour:
The resulting shield doesn't have any enchants anymore.

Expected behaviour:
The resulting shield should be decorated AND have the original enchantments, just like in Java:

Additionally, adding a "standard" banner to a shield in Bedrock works exactly as expected, with it retaining the enchantments when combining them in the crafting grid.