HI Ethan,
I suspect this is happening because of the breaks in your data.
All Three data sets use the same set of Y values.
Ux has data for the first two Y values, an these two data points are connected. There is no data for the next five Y values, so they are left blank, and do not generate a connector.
Uy also has data for two consecutive Y values, then a mixture of empty cells and isolated single data points, and the chart exhibits the same behaviour as above.
Uz differs in 'data spacing,' with three consecutive Y values having X data values, which are connected by lines, followed by a single isolated data point displayed with no connection to the empty cells between it and the third data point.
You can get connecting lines between all data points in a series by making a different chart for each series, and leaving no gaps in the X and Y pairs in each data list. With care,those charts can be stacked with the Y and Z charts showing through the X chart. the care to be taken is mostly a matter of matching the size of each chart so that each has the same scale (and the same limits) for each axis), and removing any unnecessary details that are the same for each chart, but would be difficult to keep aligned in all three charts.
Others may have a simpler solution. This one is a bit complicated and finicky, and not one that I've used recently.
Regards,
Barry