I am fighting with a HATCH and PL-BOUDARYs creating - editing too. I can imagine like a dozen ways how to edit HATCH, none of those is without any issues.
I am recommending to stay with GRIP-EDITING for simpler edits. But there is like 5 ways how to use them... I suggest to TURN OFF hover menus and to control editing by CTRL key. See the SCREENCAST. Set it by the GRIPMULTIFUNCTIONAL system variable.
For more complicated edits you gonna need restore a boundary first, then edit a polyline. You can use some routines - probably the best one was written by _gile, found HERE.
And little code by me - to restore boudary of your double hatch - used in screencast above.
(defun c:hpass2one ( / ss en i)
(if (and (setq ss (ssget '((0 . "HATCH"))))
(not (command "_.-HATCHEDIT" (ssname ss (1- (sslength ss))) "_B" "_P" "_Y"))
(setq en (entlast))
)
(repeat (setq i (1- (sslength ss)))
(command "_.-HATCHEDIT" (ssname ss (setq i (1- i))) "_AS" "_s" en "" "")))
(princ)
)