There are additional recipes in the Soul Binder on JEI when you left click on a soul vial in JEI. The recipes says you can use either a soul filled vial and a soularium grind ball or just the grind ball to make an empty soul vial and a vial of whatever soul filled vial you left clicked on. There are a handful of other recipes just like that where the output does not match the input.

Made a fresh mod pack with the same versions just to make sure no other mod, config, or script was interfering.

• EnderIO: 1.12.2-5.2.61
• EnderCore: 1.12.2-0.5.76
• Minecraft:1.12.2
• Forge:14.23.5.2854
• JEI: jei_1.12.2-4.16.1.302
• SpongeForge? no
• Optifine? no
• Single Player