Hello,
For the last point, I advise you to ALWAYS test any update (HikaShop, Joomla or else) on a localhosted copy of your website BEFORE do it directly in the online shop.
For the issue itself, we will need more elements to understand situation, like :
Does your order with issue is status updated or not ?
Do you check in the log file, if there is any clues to your issue ?
Do you try to get some elements from the payment platform to see the differences from a "normal" order with "unfinished" order ?
Other useful elements that can leads us to help you quickly.
Note : Tutorial about the
payment log
Awaiting news from you.
Regards