Can you give any example for the invalid JWT? If you receive 400 code, your JWT Token might be malformed. For example;

{
  "sub": "1234567890",
  "name": "John Doe",
  "iat": 1617201283,
  "scope": "read:data"
}

This token doesn't have "write:data" right. But if you send

{
  "sub": "1234567890",
  "name": "John Doe",
  "iat": 1617201283,
}

This token might be considered as malformed.