Why do the pronounce it masorti when the correct word is masorati?
I guess it's like people like to called Sfardic Jews "Sefardim" instead of Sefaradim. It's also like people say parsha instead of parasha.
I usually say Masorti although I am against leaving out the a that many people like to omit from Sefaradim and parashah. I do leave out the e in Sefaradim sometimes. If I see it spelled in Hebrew with the vowels, I would say Sefaradim and not Sfaradim because I say the sheva when I see it unless it's a word that I'm accustomed to say it without the sheva.
Speaking of that, most people think machloket is how you say dispute. But it's spelled machaloket in Pirkei Avot. Maybe it's an optional thing like gefen and gafen. But I hold that it is not optional to leave out the a in Sefaradim and parasha.
What about Machshev, computer? Some people think it's called Mechashev. They think the plural is Mechashvim. In modern Hebrew it is Machshev and Machshevim. But it may be the other if you use Biblical vowels.