Only a small area of the search box is clickable/highlighted for searching See screenshot:

Works fine in inventory/normal crafting bench

Edit: When search bar is on the right it's actually too big, though that's much less annoying than too small. See second screenshot:

Have you resized the minecraft window while the GUI was open?

Nope I just set the window size when I launch the game.

I tried but I can't reproduce this bug. If anyone knows how I can reproduce this.

You're doing it on the tinkers construct crafting table right? It doesnt happen on normal crafting tables.
You could try it in the All The Mods: Expert pack, maybe theres some other mod causing a conflict of some sort.

Its really not a huge issue though if you don't want to hassle with it! ^^;

Ok I will try the Modpack. Hopefully I can reproduce the bug ^^

Since I where never really able to reproduce the bug and the version is probably outdated anyway I will close this issue. Feel free to open a new one if the issue persists in newer versions.