I am driving a July 2018 Model X, HW2.5, 100D. I am now on software update 2019.40.2.1 and I have had the weaving since 2019.40. It does not seem to do it on straight autopilot (pull the auto drive stalk back twice with no set destination), but it has gotten worse with running navigation with autopilot. There is no weaving on straight autopilot, it keeps the car perfectly centered in the lane... at least, in my experience.
Initially I read on this forum that it was a modification for people complaining that the car kept a straight line when passing large trucks or big rigs, when we would naturally move a little away to give the truck a few more inches or room. However it is now randomly weaving slowly, back and forth about 6 inches or so, even when there is no traffic. Does not do it all of the time, which is confusing. Most of the time it is mildly annoying. However my girlfriend and I were driving back from Fresno, California to the SF Bay Area late on Saturday and the weaving seemed to get worse. I was really tired from driving all day, and I tried several times to initiate Navigate on Autopilot but the weaving seemed to get worse, and in a couple of times, the car actually chattered back and forth violently when I initiated the autodrive, my girlfriend got upset and scared, and I had to stop it and drive "by hand" the rest of the way. Could not trust the car. Perhaps the car was tired, too?
Perhaps I should have pulled over, taken rest and then reset the car software to see if that helped.
This weaving and chattering has been described elsewhere in these forums and several suggestions were made that perhaps it was the results of having different tires front or back (some people replaced worn tires with just two for the front and rear, rather than replacing all of them at once). Others have suggested that perhaps the tires became misaligned or unbalanced and it seemed to improve the driving characteristics with correcting the defect. Others have suggested it is a problem with the drive train itself. I have not rotated the tires at all yet (at 20,000 miles) so I have a service appointment in 2-3 weeks to see if tire rotation and service helps.
Somehow, though, I think it is a software problem. The CPU is slow to process data, and overreacts with an oscillation behavior when it is trying to navigate and watch traffic and keep the car centered and away from other obstacles.
Mike P
