kdeconnect v1.6.4 KDE Neon 5.10.0 On my Huawei Nova Plus, locking the phone and unlocking it (via the fingerprint sensor, if it matters) while in the kdeconnect app showing the touchpad, trying to use the touchpad will result in heavy mouse jitter until the app is restarted.
It's true that it jitters after unlocking the device, but only for the first few seconds. This is because KDE Connect reconnects again after you unlock the phone, causing the connection to be unstable for a bit. For me, however, it works without problem 2-3 seconds later after unlocking. Does this happen to you permanently? Can you provide a way to reproduce it on my devices?