Delay in alert generation for deadman kind of task

Hi
I am seeing intermittent delay in alert generation and I am not able to figure out the reason for it. The delay is about 1 min 30s -2 mins. Its not a big delay, but I would like to understand the reason behind it.

My tickscript is like this-

var template lambda
var orgId lambda
var whereFilter = lambda: template AND orgId

stream
|from()
.where(whereFilter)
.groupBy( 'template', 'orgId')
|stats(30s)
.align()
|derivative('emitted')
.unit(30s)
.nonNegative()
|stateCount(lambda: "emitted" == 0)
|alert()
.stateChangesOnly()
.crit(lambda: "state_count" > 10)
.log('alerts.text')

No files or tests are named. Start by reproducing the supplied tickscript and measuring the timing through stats, derivative, stateCount, and alert; done means identifying and documenting the cause of the reported 1m30s–2m delay.

Written by the indexing model from the issue text.