Is it safe to assume that nearly two years later, the MH website is still buggy and one should continue avoiding use of it to book flights?
I use the MH website all the time for my flight bookings and have never had a problem. There's only been one time when the whole site was down (I think it was Feb last year) in the last 4 years that I can remember.
Follow-up: I was only able to resolve my reservation issues last year through the help of social media. I'd only use MAS again via a travel agent. I got zero help from MAS USA. YMMV