After some time the runner will become not healthy and will be disabled

We have gitlab runners in k8s, After some time they become unhealthy and stop executing jobs.

**gitlab runner version**: 11.7.0 
**runner log**:
ERROR: Checking for jobs... forbidden               runner=9b53075c
ERROR: Runner https://*********/9b53075cde724fdb8914695d662852 is not healthy and will be disabled!
ERROR: Runner https://*********/9b53075cde724fdb8914695d662852 is not healthy, but will be checked!
ERROR: Checking for jobs... forbidden               runner=9b53075c
ERROR: Checking for jobs... forbidden               runner=9b53075c
ERROR: Checking for jobs... forbidden               runner=9b53075c
ERROR: Runner https://*********/9b53075cde724fdb8914695d662852 is not healthy and will be disabled!