AWS t2.small example reduces some time by a small amount of time

Question

I am using an aws t2.small instance in ALB and have set up data transfer alerts if the host goes down, which collects data from AWS load balancing.

once every 2 days, I get a warning that the host counter is below 1. but it is automatically restored within 10 minutes. below is the aws cloud-watch metric for load balancing, it also shows that the host has been reduced by a fraction of the time.

I cannot understand why this is happening, and is there a way by which we can debug it.