What I expected to happen was...: when i used replaceitem with my seccond command block it should of replaced the item in the shulker What actually happened was...: it gives me an error that theres non container there Steps to Reproduce:

1. place a shulker box near a command block

2. in 1 command block write replaceitem block (here the coordinates of the shulker box)slot.container 0 air

3. place a second command block and write replaceitem block (here the coordinates of the shulker box) slot.container 4 air

4. set both command blocks to repeat and always active and unconditional and previous output

also this is on a realm