Hi Spazms, thanks for checking out the mod! I double checked some things with an inventory size of 800, and did not find unexpected issues.
The mod stops working when the number of filtered slots it wants to set is greater than the number of empty slots in your inventory. This is a limitation of the mod in it's current form, and is something I aim to improve in the future. Increasing your inventory size, setting more quickbar slots, setting more manual filtered slots in your inventory, and carrying fewer items are ways you can combat this for the time being.
If you want to use manually filtered slots, you'll need to set them further down in your inventory than where the decon planner / fish filter is. Any slots you set after that point are "protected" and won't get removed by the mod. Any slots you filter prior to the first decon/fish slot are unsafe.
