The epoxy was applied on the outside and was later covered by insulation. Here is a picture from the EVA where they cut away the insulation and located it: https://i.insider.com/5c112efc4a8213310205a17b

I’ve worked with epoxy quite a bit, and delaminating is one of its failure modes. That is, sometimes it flakes off cleanly without leaving much behind.

Having said that, it’s hard to believe that there wouldn’t be traces of epoxy inside that very rough hole, or in the bare metal exposed by the drill bit. So it seems odd to me also.

Once in KSP Iinstalled MechJeb (a modded autopilot component) upsidedown and my rocket failed in precisely this way, trying to make a u-turn right off the launch pad. Pretty funny to see it happen IRL, since nobody got hurt.

I don't think you can attribute this failure to a political system. Space is hard. NASA's Genesis sample return capsule also failed due to an upside-down sensor[1].

Fun fact about the Proton M failure: the sensor was designed so that it could only be mounted correctly, but apparently it had been forced in the wrong way somehow. Possibly with a hammer. From [2]:

By July 13, investigators simulated the improper installation of the DUS angular velocity sensors on the actual hardware. As it turned out, it would be very difficult to do but not impossible. To achieve that personnel would need to use procedures and instruments not certified either by the design documentation or the installation instructions. As a result, the plate holding the sensors sustained damage. Yet, when the hardware recovered from the accident was delivered to GKNPTs Khrunichev, it was discovered that the nature of the damage to the plate had almost exactly matched the simulated version.

[1] https://www.newscientist.com/article/dn9331-crashed-spacecra...

[2] https://www.russianspaceweb.com/proton_glonass49.html#culpri...