Yes, this absolutely is still happening. I am on my second 5X. I requested a second replacement. Below is Garmin's response. I will never be buying another Garmin watch. $600+ for a watch from a company that states a major flaw is to be ignored?! Many have reported that the cracking/ chipping of epoxy does indeed have a negative impact on performance. Insane!


The issue that you are experiencing with the epoxy is going to continue no matter how many times we exchange your Fenix 5X. The cracks are only cosmetic and all watches we've tested continue to operate normally. The superficial cracks do not affect the water rating. Since the cracks are on the back of your watch, they are not visible during use, do not impact the performance of the watch, and replacement or repair is not necessary.

Thank you for choosing Garmin,


Chris

Product Support

Garmin International

That doesn't sound acceptable at all, as any defect in that surface will lower the accuracy of the optical sensor as the surface becomes less clear and light transmission to the photodiode is impacted, they should keep replacing it for you or use a material that doesn't fail so they don't have to. It sounds like the cracks will propagate, eventually causing complete failure.

The point is that there is a defect, it is like buying a new car and your front bumper paint starts to crack after 2 months, then you are told by the manufacturer that since the cracking paint is not visible from the driver seat, and does not affect vehicle performance or safety that a repair or replacement of the bumper is not necessary.

Well just to let you all know my fenix 3 sapphire hr has a crazed sensor and it affects the reading. I completed a 6 week trip to NZ where I had to put mozzie spray on every day, and the sensors have now crazed over like a car laminated windscreen that was hit by a big rock. I inspected it with a high power magnified and it doesn't appear to have cracked all the way though to the leds or the chip, however the deep crazing is across the leds and the sensor chip and it does affect the hr monitoring.  I used to get all activity hr monitoring and sleep perfectly, but now if rarely catches sleep and randomly catches sport activity and is latent when it does. I have tried to polish the cracks out with a dremel buffing wheel and jewellers rouge, it helps a little but the crazing is optically deep and not just surface. Very disappointed with this part of what was a 600 dollar (450 British pound) watch. My old fit bit hr monitor worked though the same environment but the rest of it fell apart after a year but it was 70 British pounds! I wont replace the fenix with another unless the issue is fixed.

As far as I know Garmin we're replacing units with the cracked hr gell.....but you've had lots... with the same issue.... I've never had the issue luckily..... Perhaps ring them again and suggest you pay extra for an upgrade...... I've upgraded from a Fenix 3hr....to a Fenix 5x....to a Fenix 5X Plus... because of faults I found and reported.. and helped with .(had seven Fenix 5x's) ... I only had to pay the extra. (Garmun UK) 

I'd ring them again.... 

The cracks do not appear on every watch, they seem to come because the resin can not take sunscreens or insect repellents.
I had the same issue on my watch and I got it replaced.
I have now put on a round clear tape on the back protecting the sensor.
The tape is cut out of self-adhesive cover foil.
I take it this will not damage the sensor, and it will help keeping chemicals away from it.

It is never a good idea to bring plastic in contact with sunscreen products, as the filters and the oils used to dissolve the filters can penetrate into the plastic and make it brittle. As it is also not a good idea to bring sunscreens in contact with coatings (of your bike or car), I always wash my hands and the area of the watch after using a sunscreen.

https://support.garmin.com/en-US/?faq=yAgOpDYLCe4ftSa9k0dQx7