Sorry - I should have specified that I have a smart keyboard.
Anyway, I have just gone through my settings and set move tool aspect constrain to always constrain. I looked all throughout the interface in the app to find this setting earlier on, but never realized there was even a cog/settings icon in the welcome screen.
Coming from Photoshop, this app is such a huge adjustment - there are so many unintuitive things that really get frustrating on top of all the random crashing which causes me to lose my work! I have faith that it will get better with updates, but I just wished it was slightly more intuitive.
Thank you for your responses!