I've had a Garmin Edge 200, Garmin eTrex 20x, Lezyne Macro, Garmin 1040 Solar, and now a Garmine 840. The 200 and eTrex worked flawlessly for years. In order of reliability:

From worst to best: 840, 1040, Lezyne, 200, eTrex 20x.

The 840 has frozen mid-ride three times. In all cases it froze on the map screen navigating unfamiliar roads, and I rode some distance not realizing the screen was static. It has inexplicably changed fields and even the layout of the second data screen, mid-ride. A friend at Garmin tells me this is not possible. BS. I'm a software engineer. It's a frickin' bug, possibly hardware related.

The 1040 froze once mid-ride, again freezing on a map screen. On several occasions is ended navigation inexplicably mid-ride. Fantastic battery life, at least.

The Lezyne gets dinged mainly because it didn't handle routes that crossed themselves. I think the intended purpose of this device is urban navigation in conjunction with a smartphone, using the Lezyne mapping app. Sort of a fail IMO, as a navigation device.

The Garmin 200 display blacked out once under extreme sun, but it recovered once shaded. The unit functioned fully during this time. Navigation was dirt simple - just keep the dot on the black line. Short battery life. Outdated of course.

eTrex 20x wins for robustness. Heavy, clunky UI, outdated, screen hard to see in full sun, turn-by-turn supposedly worked but I never figured it out. I sold it years ago, but now wish I had it for hiking.