• VSCode Version: 1.50.1
• OS Version: 10.15.7

Steps to Reproduce:

1. Set system input source to shuangpin, before which add shuangpin as an input source.
   
2. Lock caps lock, with caps lock unlock, you will input Chinese character, which is an expected behavior.
3. Input something in the integrated terminal, I can only input upper case letters. But when I input something in editor or some other application, I can input lower case letters.

Does this issue occur when all extensions are disabled?: Yes.

Actually I think it might be the problem of xterm.js. Xterm.js might decide the letters by cap lock. This is not as expected with shuangpin mode.