Did anyone break the tab holder on the back of the device?

No and I doubt this would snap with normal use. I suppose if it broke you would need to find a new case.

Something like this, for example. Glue firmly with a good special adhesive.

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If it`s on warranty there`s a high chance that Garmin will replace your device. I got a brand new one as a replacement unit.

Funny, it seems that there`s a new revision of Explore 2, which can be distinguished by an additional hole on the back cover (to the top and right from serial number sticker). And this new device seems snappier than my first Explore 2 + touch screen is more responsive and accurate.

This is interesting! 
Do both of your devices use same software version?

Yes, they do.

Another small thing that tells them apart is that there is no that 2nd additional shutdown jingle (when powering down) which was on my old device.

It kinda fell apart on its own. I had it in my Garmin mount on one of the gravel rides and when I took it out it was broken. Luckily it still held the device quite firmly.

Seems like quality :D

I am going to buy explore 2. Is any way seller can recognize new revision even if it packed?