Problems with shulker boxes in bedrock

I'm trying to convert a resourcepack that changes shulker boxes from java to bedrock, but I got two weird issues (the premise being I'm not very familiar with bedrock).

In short, as you can see in the attached image some of the shulkers are only "half" textured. The shulker placed in the world works just fine, but in the hotbar and inventory is missing the top part. Not sure why, works ok in java.

The light gray shulker box texture is not applied at all. I saw afterwards that on Bedrock the texture file is actually called shulker_silver.png , but even with this name it is not applied, so I'm probably missing something trivial here...