@balihr, besides the PPE/OPC trace-logs were there any debug-logs thrown an/around the time of the missing shipping-address(es)?

Depending on the site in question, i.e. how 'buggy' it is, you might consider installing Report All Errors and setting it for all non-duplicate-constant messages on the storefront. That way, if/when the issue occurs again, there would be additional breadcrumbs left to hone in on the issue's source.

BTW, which sub-version of zc156 is in use?