I get constant "Sorry, an unexpected problem occurred" when I am trying to finalise the postage labels, and they cannot be generated. This has been on-going for a probably two years now. It doesn't happen every time I try to purchase postage, but most of the time.
Any idea when this problem will be fixed?

Still happening. Most of the time I get "Sorry, an unexpected problem occurred." and have to find and regenerate the label. Wish they would sort this instead of tinkering around with the appearance of the site.

I reported this on 3rd October. The reply of 30th Oct included:
"There is a technical error being investigated with our I.T team affecting the label creation process, the work around when this occurs is as you described to locate the orders and regenerate paperwork.
Please accept our apologies for any concern this has caused our I.T are working to fix the problem as a high priority."

I get a lot of errors with "Sorry, an unexpected problem occurred." when trying to print labels.

I reported something similar, specific to label printing, back in June. Nothing happened, and it is still happening.