An update: Has found out that the reachability check failing is correlated to allmost full network utilization on the instance.
Turns out that after our instance migrated to new underlying host the network driver used was not compatible. We upgradet to newest AWS Network driver and our problems were resolved.
Instance reachability check failed - two days in a rowasked 3 years ago
My EC2 Instance reachability check failedAccepted Answerasked 2 months ago
Can I get email when instance reachability check failedasked 2 years ago
create clone of ec2 instance in two AZasked 6 months ago
Instance reachability check failedasked 6 months ago
Instance reachability check failed on ec2 ubunut 18.04asked 6 months ago
Ec2 Instance reachability fails every time.asked 10 months ago
System reachability check passed Instance reachability failed!asked 4 years ago
Instance reachability check failedasked 2 years ago
aws ec2 Instance reachability check failedasked 10 months ago