Placing and using lockers works fine. But whenever I mine/remove lockers with a tool or by hand, minecraft crashes. Any interpretation/suggestion helps. :) Let me know if there is any other information I can provide.

https://pastebin.com/a80X5uqH

I haven't been able to reproduce this. Maybe another mod is causing interference?

I've tried running Better Storage Too against all the other mods (82 of them) one by one and found that the issue ONLY happens with OptiFine_1.11.2_HD_U_C7.

Since I also have ShadersMod v2.6.1 installed, I tried running Minecraft with Better Storage Too and Optifine withOUT shaders and Optifine WITH shaders (tested on two shaderpacks: Sildurs Vibrant Shaders v1.17 Lite and SEUS Renewed v1.0.0).

On a new map, Optifine withOUT shaders allows me to break lockers without issue. However, WITH shaders causes the server to crash. When testing on old maps, it doesn't matter whether I have shaders on or not. Both will cause a crash. The only way to prevent the issue from happening is by removing Optifine from mods folder.

You might be able to reproduce it this time and be able to trace the bug that's causing it. I'll eventually bring this up with Optifine and Shader authors too. In the meantime, I will just have decide between visually stunning Minecraft and this wonderful storage solution.

Let me know if there is any other information I could provide that may help.

Optifine is well known for breaking mods. It does a lot of in-compatible changes to the rendering of Minecraft.