I would pretty much bet the bank on user error as opposed to a “bug”. No offense. But it’s impossible to know for sure without looking at the actual project. If you’re able to upload it somewhere, I could take a look. But with that said, BEST is really only of any value or use when you have things such as massively scaled vector graphics or fonts or the likes. Otherwise there’s little to no reason or advantage to switching. It’ll in fact most likely take a lot longer to export with no tangible difference in actual quality.