Seconding the issues on the Load Balancer and 502s. We moved our app there earlier this year to take advantage of GKE and just sort of put up with random 502s (especially during deployments, which are supposed to be zero-downtime). We contacted Google Support but they were unable to help and said that yeah, some percentage of dropped requests is fine. I suppose it's something with our Rails app or configuration, but no one was able to help and I decided to stop wasting time trying to fix it.

They have more-or-less gone away now but several months later it leaves me with very little confidence in GLBs and quite scared to change anything around.