Edit: I'm just seeing this us an older thread. It popped up in a search and my head assumed it was a recent convo and I typed out a reply. Regardless, perhaps someone else searching threads will find it useful.
The Eaton (parts adopted by Harrop) does momentarily lock/unlock/lock when you change directions. For most this is a non-issue and they are a great option. They did have issues with electromagnets on early variants, more specifically the retainer. We ran them on Carl's rock-crawler in UROC competition nearly 20 years ago now. They have since improved design imo.
After 44 years there are over 500,000 (and that number is dated) ARB Air Lockers out in the wild and being used in some of the most austere conditions, Baja 1000, Dakar, King of the Hammers and the only vehicles to regular travel to the North & South pole do so with ARB's installed in place of OE e-lockers. The trucks we drove across the long axis of Greenland, ARB equipped. There are years the winners of all classes of KOH have been ARB equipped.
As such, you will absolutely deal with or hear of failures, nearly exclusively air supply. Many of those cases are blatant instal error, air supply lines out the bottom (yes bottom) of the diff, plastic airline (which the modern black lines is faaaar superior to the blue line) routed next to spinning shafts, hot exhaust, etc. But o-rings do fail after time and they should be on the same service interval as knuckles for example. We stock dozens and have sold hundreds (more appropriately thousands) of ARB's (and hundreds of Eatons, Auburns, Detroit, LockRights too) over the past 30+ years. They can all fail.
There are in fact plenty of documented cases of Harrop/Eaton failures/issues, again just as there are with ARB. It's my opinion that when we see over a half million Eaton's being used under the same wide range of users... stories like these below will be even more prolific. Fwiw these comments are all from a couple threads on FB.
(Recent FB comments on Eaton/Harrop e-lockers)
Now, for the OEM cable/e-locker. It has its own issues undoubtedly, particularly the 9.5" variant used on the 6x/7x/8x full-float and other semi-float/IFS/IRS applications. The issue is more related to the axle shaft failing and/or twisted splines between the locker's lock sleeve and the side great, making the repair very difficult and can require cutting a hole in the axle housing to resolve. This has been documented on Mud by myself and others over the years.
(This is where the 9.5" locker struggles for some)
But, for most, the OE lockers are fantastic, cleanest integration and parts are somewhat readily available.
Important to note,
some newer application Land Cruiser (and other) OE lockers from Toyota are no longer the same slide actuator/sleeve design rather also electromagnetic but not using the Eatons ramping pins so they don't unlock with direction change. Jury is out on how well they last over time but thus far is been seemless operation. The rear could be retrofitted into the 80 rear without too much headache, the front is a different story.
(New style 9.5" OEM locker)
I have or have had ARB's, Eatons and OEM cable & e-lockers in dozens of personal/project rigs. I can't think of one situation I regretted the choice relative to the way I used the vehicles. Most of my stuff now has factory installed e-lockers with ARB being the runner-up and OE cable lockers being the least common but favored variety. Yes, I'm the luddite that would love a cable locker option in the 200 Series
