What can trigger EC2 updates aside from Maintenance Windows

Question

I am running into something that seems happening without a trigger.
I have 111 EC2 instances, a mix of various versions of Windows and Linux.  Everyday at about 18:30 GMT a seemingly random combination of servers patch.  Nothing that I can find is triggering it.
There are 4 maintenance windows, all currently disabled.  And they were not for that time anyway.  
Is there something else I can look at?  Where\What else can trigger patching?  It appears that I am missing something.
Can anyone here shed any light on what's going on and\or what I'm missing\did wrong?

Answer

Holy cow, there are jobs there and that seems to be the source.
I never made these, you even know where they come in at\from?

Answer

Go to **Patch Manager** (it is under **Systems Manager**) and see if you have any **Recurring patching tasks**.  If yes, then click into each one and see what it's _targets_ are, to see if this is the source of the behavior you are seeing

What can trigger EC2 updates aside from Maintenance Windows

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