I replicated this in a fresh instance with only JEI and Smart Backpacks.
Steps to replicate:
1) Get any backpack, a Pulling Upgrade, and a Compressing Upgrade.
2) Place the Pulling Upgrade and the Compressing Upgrade into the upgrade slots of the backpack.
3) Right-click the Compressing Upgrade while it is in the backpack's upgrade slot.
4) Crash to desktop.
I noticed that if I placed only the Compressing Upgrade in the backpack, then I could right-click it and access its filter slot. But when I placed the Pulling Upgrade in first, and then the Compressing Upgrade, then that caused the crash when attempting to access the Compressing Upgrade's filter slot.
I replicated this in a fresh instance with only JEI and Smart Backpacks.
Steps to replicate: 1) Get any backpack, a Pulling Upgrade, and a Compressing Upgrade. 2) Place the Pulling Upgrade and the Compressing Upgrade into the upgrade slots of the backpack. 3) Right-click the Compressing Upgrade while it is in the backpack's upgrade slot. 4) Crash to desktop.
I noticed that if I placed only the Compressing Upgrade in the backpack, then I could right-click it and access its filter slot. But when I placed the Pulling Upgrade in first, and then the Compressing Upgrade, then that caused the crash when attempting to access the Compressing Upgrade's filter slot.
Forge: 14.23.4.2760 Crash log here.
I hope this helps!