When making terrasteel, sometimes the particles stop at the very last second and won't change the materials used to craft it. There is no crash or the game freezing, except the terrasteel production...

Here is the mod list: http://pastebin.com/6dRMNFeH
Here is a log: http://pastebin.com/yUTqUUsc
This happened multiple times, but not every time.
I am using the latest version of Botania (R1.6-187).

Would tick skipping mess up the crafting process @Vazkii?

Yes, server lag might cause this.

Do you just barely have enough mana? It might be almost crafting, then the portal steals the mana or something like that...

I'm pretty sure I had enough mana... Even if I didn't, it would have finished because my manastar showed that I was producing more mana than I was using before activating the terrasteel production... It did not progress at all...

If you take the items off and put them back on does it work? Do you need to reload the world? Restart the game? Single player or multiplayer? Are you using MCPC+/Cauldron? Fastcraft? Mystcraft? Where are you pulling mama from with the spark?

I am using Fastcraft and Mystcraft. This is singleplayer. I found out that this is a visual issue because the mana is not being drained even though it looked like it...

Does this always happen or did it only happen once? Do you have more screenshots of the setup? What version? What mods? Got a log?