minecraft version: 1.20.4
magic version: 10.9.3-df02033
server: git-paper-435

When a dropped shulker box is pushed by Velocity class, its container NBT is deleted.

This is the spell which is used in the above video.

This doesn't occur for any other container items like chest, barrel, etc... .

I can not use English well. So i'm sorry if my writing is difficult to read.

Hello, thank you for the report!

I have been unable to reproduce this. I tried with your exact setup- which is actually a little weird. You're making the shulker box itself cast a spell... I can't imagine that would happen under normal circumstances.

I also tried just using the "Push" spell on a dropped box.

In both cases the inventory stayed.

I believe there's something weird going on since you have it on video, but I will need to be able to reproduce it (make it happen again) to have any chance of fixing it.

Can you please tell me what version of magic and server you are using? The output of the following commands would be great to see:

/version
/magic

Thank you, sorry it's taken me so long to look into this!