It is the clunkiest I've encountered. Discount codes haven't worked for me in well over a year, with 2 browsers. I did finally figure out that their order page breaks (hit button, nothing happens or throws an error) with ad blockers or extensions of any kind, including my password manager, enabled in Firefox. Something with captcha. Who knows, but it is amateur hour programming.
After several years of complaints, numerous posts from a lot of folks here about problems placing orders, I guess they don't care they have a crappy web ordering system. I've gotten used to it, temporarily disable all Firefox extensions to place the order or try using Edge with no extensions.