For what it's worth, this issue is also present on Debian 9, Fedora 25, Arch, and Windows 10.
One interesting thing I noticed - when it's stuck in the "scroll mode", the cursor appears to move semi-normally, but as I move my finger from the left to right, the cursor freezes when I reach the center of the trackpad and only scrolls. While I can't reproduce what causes the initial erratic behavior, I am able to reproduce this action.
For what it's worth, this issue is also present on Debian 9, Fedora 25, Arch, and Windows 10.
One interesting thing I noticed - when it's stuck in the "scroll mode", the cursor appears to move semi-normally, but as I move my finger from the left to right, the cursor freezes when I reach the center of the trackpad and only scrolls. While I can't reproduce what causes the initial erratic behavior, I am able to reproduce this action.