Gangjee, four-under in 13 holes with five birdies and one bogey, dropped three three shots in the last five holes, including two on last two holes for a 71.
That saw him finish the third day at tied 34th, two places up from his second round position, but way worse than what looked possible a few holes earlier.
Gangjee birdied first and second and then three in a row from 10th to 12th.
Tyrone Van Aswegen fired a six-under 65 on Saturday and moved into first place after three rounds.
Van Aswegen jumped ahead of the field with an eagle-3 at the par-five 17th and finished at 13-under 200, one better than Bio Kim (64), Woody Austin (66) and second-round co-leader Billy Horschel (69).
Two shots off the pace are Shawn Stefani (66), Cliff Kresge (68) and Jim Herman (70). Two-time US Open champ Leen Janzen shot a 66 and is only three off the lead.
