Garageband won't play mid-note

During playback, when I skip the playhead to further along in the song Garageband (version 10.1.0, on a Macbook Pro Retina Early 2015) will only play a newly hit note after whatever I'm in the middle of.

Which means long-held synth keys won't play unless I happened to record another piano key being hit, or take the playhead to the very beginning of when I hit that note and have to listen to it all instead of jumping to a part of the song I want to work on. All of the sounds are from Garageband instruments.

It's incredibly frustrating and slowing down my work process. Any ideas?