Bad cursor synchronization in timeline

Some things from your log

[Debug ] Mlt::Controller::setPreviewScale 1280 x 720

I see you are using preview scaling. If you do not make and use proxies at the same resolution, this can slow things as explained in Preview Scaling

[Debug ] MainWindow::setAudioChannels 1

Did you really mean to change your project to mono (using menu Settings > Audio Channels)?