using flip on a clipboard with architecturcraft slopes in it crashes the server and client upon placing it

[Alaking]

like in the title, I place a structure containing normal blocks and architecturecraft slopes and copy it
pasting it without any changes works fine
//flip and then pasting it crashes

additional mods are fastcraft, ftbu and ftblib on the server with the 0.0.4 version
crash-2023-07-27_19.16.31-client.txt
crash log is attached

[gtosh4]

Hey, so I haven't tested flip much. I fixed the crash in https://github.com/GTNewHorizons/worldedit-gtnh/releases/tag/v0.0.5, but I'm not sure the flip is working. I tested all the individual rotations and they seem correct, but there's something else going on with flip that makes it not look correct.