Modpack version
1.65d

Can the issue be reproduced?
Yes

Logs
Here

Issue
This issue was reported by a user on Discord running into a crash when using the RFTools Builder's preview function while using a shape card. The issue was already reported to McJty and is known there; though the cause is unknown.

I asked the user on Discord to try and reproduce this in an instance with just RFTools in there and provide us with an additional log.

For reference: McJtyMods/RFTools#1961

After testing (by the reporting user) with an instance using just RFTools, and McJtyLib it is reproducible. Rendering the first preview goes fine; the second one crashes the game.

Corresponding logs: here

The issue was reproduced, found and fixed by McJty and will be fixed in the next release.

As Frikkle said, this was fixed by McJty and the mod has since been updated in version 1.66c (commit 0b33096) ^^