Midi input lagging Mac mojave & Musescore 3

Hello, I was happily using Musescore 2 with midi input but I wanted to try updating to musescore3 and then it wasn't compatible with my mac iOS so I upgraded to mojave OS and upgraded musescore at the same time. Now when I plug in my midi keyboard and play a bit the program seems to be getting overwhelmed and the sound starts to lag behind a lot, especially if I play a lot of notes at once. When I go to input the notes with real-time advance, the metronome beat sometimes goes wrong by about a half beat while I'm playing the notes - it's very confusing! When I play a chord the notes sound individually and the program takes a while to catch up.

Before, I could just select a note and play away on my keyboard for a bit improvising something or trying out something before inputting it, now it gets overwhelmed and lags. Is there a reason for this? Am I doing something wrong? Should I go back to version 2 for a while?

Thanks
Jayson