Hi,
You're the first one reporting an issue with the product edit page with the 6.2.0, so it's hard to provide a helpful answer.
Regarding the "Unknown format specifier " "" error, please activate the "debug system" setting of the Joomla configuration and try again. It should display an error message with more information about the issue. That will allow us to understand what's going on so that we can tell you what to do.
It's probable that the error you had before the update what the cause of the problem and that updating HikaShop didn't change anything to the problem and saving the product just made the problem worst with that product.