Mock Server 502 Bad Gateway

We have a postman Mock Server that has been in place for over a year.

Today we are receiving lots of failures when sending to this and get response:
502 Bad Gatewaynginx

This is very sporadic - it seems to work around 9 times out of 10.

What causes this error for Mock Servers?
Is there anything we can do to prevent it?

There have been no other network issues on our side.

This had not been an issue in the past and there have been no code changes or anything on our side. Is it possible a recent Postman update might have caused some issues?

Many thanks,