I get an error changing the example request from 68 to 67 characters:

https://api.left-pad.io/?str=paddin%27%20oswalt&len=67&ch=@ {"message": "Could not parse request body into json: Unrecognized character escape \'\'\' (code 39)\n at [Source: [B@38ac0021; line: 2, column: 21]"}