A hatch, when you apply it to a contour, is a container basically, means lines are combined into one entity.
But when you use explode tool, the hatch container is separated into its multiple single entities, that's what you have.
Undo is possible, when you recognize this mistake, but it's time consuming too, as you have to press Ctrl-Z for every single hatch line.
To make selection easier, you can drag a right to left selection window (the green one), which selects all intersecting lines.
Or select the whole contour with window selection and then deselect all lines which should stay before deleting.
Armin
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