What could cause a high loop delay?

Hey guys,
we’ve deployed our app with PM2 and running it on a 4 core VPS system (so we scale up to 4 instances of our app). After 1-2 days, I have a high loop delay in one of our processes:

The problem is, that this happens only to one instance and it’s every time the same one (instance 1). So instance 0, 2 and 3 have a loop delay <1ms.

On instance 0, we are running a a daily cron job which deletes old data from the database. The cronjob is visible in Kadira (about 10:00am):

So instance 0 is the only instance which executes code the other ones won’t execute, but only instance 1 is the one with a high loop delay.

I’ve already checked via console.log if instance 0 is the one which executes the cronjob, so the problem seems not to be the code of the cronjob.