I am using Geyser-spigot + Floodgate to allow bedrock users onto my server. It is normal for bedrock users to not be able to see custom textures/resource packs for Java server and use such items, however, having custom items plugin + knokko core on the server has caused a conflict with the bedrock player whereby the crafting table does not hold recipes, ie if you click on make an iron chestplate the iron ingots flash on and off and leave an empty crafting table, if you want to craft something complex like a sea lantern and don't know the recipe then the bedrock user cannot make the item as it changed the crafting table in such a way as they can only use it if they drag and drop individual items into crafting slots. On disabling custom items plugin + knokko core the issue for bedrock players with crafting table was fixed. I hope there can be a fix for this at a future point as your plugin was easy to use and offered a lot of creativity and potential.

I see this is already reported on bedrock issues, but to add a bit more detail - this issue occurs on all bedrock platforms - pc and mobile phone.

What happens when you try this custom version of custom items?
https://github.com/knokko/custom-items-gradle/files/8543292/ThisContainsCustomItems.jar.zip
Does that solve (part of) the problem?

I was quick because someone else reported the same behavior before: #160
This time, I should not forget to include this fix in the regular versions.

I can confirm. This is is the same glitch that happened to me.

Which attachment? I don't think your message has any attachments.

Install Custom Items 10.5 or later to get rid of that warning.
EDIT: Never mind, CI 10.5 of course doesn't contain the Bedrock fix...
You will need to wait until I publish the next version.

This fix is included in Custom Items 10.8