See AppliedEnergistics/Applied-Energistics-2#6750.
Our toast: https://github.com/AppliedEnergistics/Applied-Energistics-2/blob/forge/master/src/main/java/appeng/client/gui/me/common/FinishedJobToast.java.

This is likely caused by this: https://github.com/AHilyard/AdvancementPlaques/blob/1.19/src/main/java/com/anthonyhilyard/advancementplaques/AdvancementPlaquesToastGuiWithToastControl.java.

(The author of ToastControl suggest using ToastAddEvent)

I can't reproduce this crash with a minimal setup (Only AppliedEnergistics2, ToastControl, and Advancement Plaques installed). Chances are another mod is interfering.
@Sakreton Are you using a modpack that I can download somewhere for troubleshooting, or is it a custom mod set?

ATM 8 version 1.1.9, i for my part could also not find a way to reproduce it. All a can say is that it only happens when the me terminal is still open.

linking for context Shadows-of-Fire/Toast-Control#31 (comment)

I can add on to this and I am able to reproduce it. I am playing on a modpack called All The Mods 8, I am on version 1.0.25, I get this crash when I try to craft things with ae2, I can reproduce it by queuing up a craft and going to a recipe page so I can get the popups for when the craft is complete, I don't know if it has to do with speed or what, I got this crash by crafting a matter cannon but I got it again with a different craft, how I tested to see if I could reproduce was I was queuing up crafts for items for the matter cannon and going to the recipe in JEI so I could get the crafting complete popups. Here is the log of my first encounter with the crash: https://mclo.gs/uFOQLT0