Garageband automatically looping upon midi input

Please.... help!

I'm using Garageband 10.3.5 on a Macbook Pro. When I input a midi track - say, a synth or drums playing in by hand, the track loops indefinitely and I have to control click on the bit to stop it looping.

Why is this suddenly happening? I've searched and googled to find a way to turn off this automatic looping feature, to no avail. Beginning to feel a bit like an amateur :/

Any assistance or suggestions would be very much appreciated. Thanks in advance.