Ian Woosnam, who lost this event in a playoff in 1997, was two shots off the lead at 11-under-par 205 along with Thongchai Jaidee and Kevin Na.
For the second straight day, Els lost the outright lead on the closing hole. On Friday his second shot at the par-5 18th found the water and his fate appeared similar on Saturday.
Els avoided the water this time, however, after his ball ended safely on top of the wall of the hazard.
He managed to play his third shot from that spot and sent the ball over the green. Els' fourth slid seven feet by the hole and he failed to save par for a bogey.
'It felt with my yardage I could get it up quite close and maybe putt for eagle but I still messed it up,' said Els. 'I don't think I've ever had to play a shot like that from the rocks but I just hit it a little too hard and my fourth shot was very, very tough.'
Els had carried a brilliant stretch of play into the final hole. After collecting three birdies and two bogeys over his first 14 holes, Els notched a birdie at the 15th to move to 12-under. He then dropped his approach inside six feet for a birdie at the following hole to match Forsyth in the lead.
At the par-4 17th, Els reached the front edge of the green off the tee with a monstrous drive. He two-putted for his third consecutive birdie and sole possession of first place at 14-under. The separation was a brief one, however, after the bogey at the 18th dropped him back into a tie for the lead.
'The greens were firm and it was tough getting to the flags, so I had to be patient,' said Els, the only two-time winner of this event. 'Although I made some mistakes I played well coming home until the 18th.'
Forsyth also found himself the outright leader at one point during the third round. The 27-year-old began the day as part of a four-way tie for first with Els, Lynn and Mikko Ilonen. He vaulted out of the gate with an eagle at the second to assume control of the leaderboard.
Forsyth struggled with a bogey at the fourth but picked up back-to-back birdies starting at the seventh to open a three-shot advantage over the field.
Things cooled down for Forsyth from that point on. He ran home 10 consecutive pars for a share of the 54-hole lead.
'Obviously Ernie is there, so he's probably the man to beat. But today he showed he is human and does make mistakes,' said Forsyth, who posted a 3-under 69. 'I think it will be pretty close tomorrow.'
Lynn, who is looking for his first victory on the European Tour, stumbled early with two bogeys and a birdie over his first four holes. The 29-year-old had four birdies the rest of the way, including a birdie at the last, to join Els and Forsyth in a tie for first.
'This is a good position to be in,' said Lynn, who shot a three-under 69 of his own. 'All eyes will be on Ernie behind me so I will just go out and see what I can do.'
Robert-Jan Derksen shot a 5-under 67 to finish three shots off the pace at 10-under-par 206 alongside Phillip Price and 2001 champion Thomas Bjorn.
Ilonen struggled with a 1-over 73 to join Mark Foster in a tie for 10th at 9-under-par 207.