Plugin is adding the 'no-cache' header

We are using EasyShip plugin in our wordpress website https://kidzparadize.sg. The website is hosted in DreamHost hosting. DreamHost run their own proprietary caching system in all their servers.

We found that Easyship plugin is adding the 'no-cache' header and using cookies for
non-logged users. This cause several errors with the current caching system which lead to 504 Gateway Time-out to our website.

The cookie can be bypassed in the caching system if we know specify the name we need to look for.

But we need EasyShip wordpress plugin not to add 'no-cache' or 'must-revalidate'.

Appreciate urgent reply as we been experience this issues quite a while. Thanks