Shipping charges not being displayed - 1.5.6.4 and Journal2

I have a problem similar to the one described in this thread: http://forum.opencart.com/viewtopic.php?f=20&t=167454

My client's site is located in Ontario, Canada and uses OpenCart 1.5.6.4 with the Journal2 theme (Version 2.6.1). Their customers are predominantly in the US, but they deliver worldwide. They have purchased the Canada Post WS/REST(Q) add-on. In addition, the standard UPS and Store Pickup modules are enabled. Store Pickup is activated only for the GeoZone "Ontario".

Occasionally (i.e. more often than "rarely") when a client is checking out, the available shipping charges are not being displayed, leaving the only option as "Store Pickup". This results in the wrong total (because shipping is not calculated). In every case so far, the customer has had an account (i.e. it is NOT a Guest Checkout), and the account details include a valid address (not in Ontario). When I attempt to troubleshoot the issue - posing as a Guest with the same address information - the shipping options are always calculated and displayed correctly.

I don't know whether the problem lies in the OpenCart core or in the Journal2 theme. I don't think it's in any specific shipping method, since none of the methods is displayed (except for store pickup) when this situation arises.

I have not updated the Journal2 theme beyond version 2.6.1 due to concerns that the updated theme may have adverse affects on the existing site with its various vQMods. If someone knows whether more updated versions of the theme might address this issue, I'd like to know.

Because the problem is not repeatable (sometimes the incorrect calculation is for an existing customer who has previously had a SUCCESSFUL checkout experience), I have no idea where to turn for help.

Thank you for your assistance.

It sounds like the shipping address is not getting sent properly to the shipping methods, causing them to not show up. This would almost definitely be due to the Journal checkout. You may want to switch to the default checkout temporarily, see if anyone reports the same issue, and then stick with the default if no one has problems. You could then start looking for a different checkout as well.

If you want to keep using the Journal checkout, you should contact the Journal team for support. They may be aware of a bug and can give you a fix for it, or they may be able to tell you whether the issue is related to their code.