JoltTransformJSON fails to validate and save specs in 1.16.2

In NiFi 1.16.2 something seems to have been broken in the JoltTransformJSON processor.

When I go to the ADVANCED page in the processor properties and enter a valid spec and input, the processor fails to validate them correctly, showing "Error occurred during validation". If I try to save it, I get "Error occurred during save properties".

I tried the same spec and input in a 1.15.3 and the same worked correctly.

Spec:

[
  {
    "operation": "shift",
    "spec": {
      "*": "shifted_&"
    }
  }
]

Input:

{
  "a": 123
}