This issue can ONLY be reproduced with items which have /metadata higher than 16. The best way to reproduce this - install Thermal Expansion and Thermal Foundation

At some point, when a player request autocraft of item which have missing items in his network will produce infinite autocrafting preview loop, therefore causing server to choke:

To reproduce:

1. Setup an autocrafting system
2. Put Signalum update kit pattern onto crafter, add all needed items for at least for one upgrade kit
3. Request 128< kits
4. watch the server (client if singleplayer) choke in memory usage while waiting for crafting request preview

After first GC on serverside:

Snapshot (nps) file -
rsbug.zip

if you did something wrong on reproduction - your RS preview thread will just crash with java.lang.NullPointerException, and server/client will not choke on, but crafting preview will still fail.
With /metadata >16 RS is NEVER able to pre-calculate missing items, and preview thread will just crash

RS Version - 1.5.31
Forge build - 2611

Serverside out of memory crash is still easily reproducable.

Should be fixed in 1.6 (I can request 1 signalum upgrade kit with all items available just fine)