Non-printable ascii characters

I am using the Zyte Smart Proxy Manager via a nodejs application and most of the time, it works great; however, every now and then it returns a page full of non-printable ascii characters. Is there a reason it does this? Am I doing something wrong? The options I am passing into the request are as follows:

url: <page_url>,
ca: <path_to_zyte_proxy_ca.crt>,

requestCert: true,

rejectUnauthorized: true,

headers: {

    'Content-Type': 'text/html'

},

method: 'GET'

Like I said, the majority of the time it works fine but every now and then I get something similar to the attached output.