Rendering error for few IPs for Cloudflare Workers


We have deployed CF worker to production as API management layer which proxies API requests to our API. Everything working well for all except me - nobody complains from our users, all the developers confirm its working well.

I do see few Exception counts on the Worker Status code chart. but its handful of exception for few millions of requests.

For me, no matter if I do HTTP GET/ POST , no matter what browser I use (or Postman), I get timeout from Cloudflare. The error message is:
Rendering error | | Cloudflare

Ray ID: 41ee2f6a2dac613f • 2018-05-22 09:18:19 UTC

Can anyone help figure out what is going on?

I must also add that problem is not present all the time. Sometimes all my requests get blocked, sometimes only requests from Postman.

Is it possible Cloudflare incorrectly identifies my requests as a threat and blocking them?