Server side block nbt tag synchronization

Hello everyone.

I have a block, which is bound to a GUI, which has text fields. These text fields can be modified to contain numbers, which are then stored in the block.

The stored nbt tags are used by another block that can access them and do something unrelated.

The issue is that this process works completely fine in singleplayer, but when playing on a server the nbt tags are straight up not saved at all.

https://ibb.co/FqPmMkv

*This is the procedure that saves the values from the gui to the block.*

Thank you very much in advance.