Versions:

1. forge-12.18.3.2209
2. rftools-1.1x-5.81
3. mcjtylib-1.1x-2.3.2
4. compatlayer-1.10-0.1.7

It happens in a clean install, when client try to render the Screen with multi-byte characters (I used Chinese characters), it freezes.
It does not crash the client nor do server think the player has issues.
It simply freezes.

How to reproduce:

1. Place a screen, make sure it has power and it is in truetype font rendering mode.
2. Type some random multi-byte characters through InputMethods.

Please:

1. Properly support InputMethods for language like Chinese, Japanese, etc.
2. or Filter out any multi-byte characters, completely.

Confirmed:

1. Disable truetype font rendering through config file can avoid this.

I don't think you can survive if you set the Screen to always use truetype font rendering.

By the way, truetype font text rendering overwrites button modules' background texture.

I'll check out the freeze. You don't happen to have anything in your log that is relevant?

Also: 'By the way, truetype font text rendering overwrites button modules' background texture.' What do you mean by that?

Nothing interesting in the log: Pastebin Link

I was going to take a screenshot to show what i mean, but I can't reproduce it in a clean environment, it might have something to do with other mods' in-world block rendering.

But copy/paste is not working for my screen input

Hmm I have trouble reproducing this as I have no clue how to input those characters into the screen gui

I can type some for you to copy&paste them in.
我可以打一些让你能复制并粘贴他们进去。

Edit: oh, you can't paste them in.

This is a world save: Puush Link
Here is a picture: Imgur Link
The screen is a creative one, it has been set to "Vanilla" font rendering mode.
The world is saved with listed mods in the first comment.

This is what i mean by that: Imgur Link
Although i can't reproduce this in a clean environment.

I managed to reproduce this bug by implementing ctrl-v/paste support for the text field

This bug will be fixed in mcjtylib 2.3.4 (doesn't require an update in rftools) which is currently awaiting approval on curse.

Note that this fix will discard those characters. I have not yet found a way to actually render them and it all depends if they are actually in the font or not

Great! that means a possible fix for this is coming?

By the way, the rftools builder breaks Colossal Chests.
I was placing diamond variant chest walls from that mod using rftools builder, the builder placed invisible chest wall blocks ( i guess they are invalid ), upon breaking those invisible chest wall blocks, they all turn into iron variant chest wall blocks.
Builders wand from ExtraUtilties2 placed them correctly.
Should i open another issue to properly report this to you?

If I can find out what's wrong yes.

Anyway for the builder thing a separate ticket is best

I think they are in the font.
A picture to prove this: Imgur Link
Windows font viewer shows them in a Chinese environment.
The font is extracted from rftools-1.1x-5.81.jar.

Edit: there is also a possibility that it fallback to another font installed in the system.