Batched overnight notices not arriving in inbox as expected

Overview:

As per the test case Loan due date/time triggers: long term.

Generally, batched overnight notices serve to send notices, based on the loan due date, with more than one ("multiple") loans in one single email. The loans are batched and sent overnight, after 11:59pm, at the rate of up to 100 notices per minute.

In this case, I noticed that the notice that should be sent upon/at the due date (3/18/2022, 11:59 PM) was only sent on 3/22/2022, 1:40 AM. This prompted me to look into the other sending times.

Attached is the overview of the notice triggers, with expected and actual reception times as per the circ log. 
Item barcode 116267661 is an original test. Item barcode 80691507 is a 2nd test, trying to replicate the issues of the original test.

Red = this really is wrong. 
Orange = These are really not the times I would be expecting - but then again, how do I know 100% that the batched notices engine is indeed set up to run at 11:59pm? And is that UTC, or is that per the timezone of the FOLIO tenant, or something else again?
Green = As expected. 4:00am GMT = 12:am NewYork.
Blue = I received this email, even though it is not listed in the circ log.

--> I don't know if there is a problem (1) with the scheduling of the batched notices, or (2) with the bached notice engine. I want to confirm that (1) is working fine (as I cannot influence (2)). 

==> Can someone please confirm:
_ that the batched notices engines is working as expected,
_ when exactly is that engine running.
Because if the engine is working fine, then the problem lies somewhere else.

Steps to Reproduce:

1. Log into Lotus bugfest
2. Loan due date/time triggers: long term.
3. Circ rule = g julies-patron-group + m book + t julies-2nd-loan-type: l julies-scenario-2-loan-type r allow-all n julies-scenario-2-notice-policy o julies-no-overdue-fine-policy i julies-no-lost-item-fee-policy 

Expected Results:

Shortly after 11:59pm each night, I get an email, as configured in the notice policy listed in the XLS.

Actual Results:

Reception times are erratic, and make me question whether the engine is working ok, or if there is indeed an issue with the scheduling of batched notices. 

Additional Information:
_Please don't hesitate to reach out to me to discuss - this is a complexe set up, and it's easier to talk it through.

_P2 (and not P1) because the emails are still arriving, even though not at the expected times.

_ Added Kitfox as Devteam to start off, to first check the environment. stephaniesbuck I don't know if/when Vega will end up involved in this.

_ On https://folio-kiwi.dev.folio.org/ I'm replicating the scenario with item barcode = 645398607547. While that instance wasn't reset, the batched notices were sent out fine at or just after 04:00am UCT. I did not try replicating in Snapshot, because that instance gets reset every day, so is not suitable for testing batched notices over several days.

Interested parties: JulieBickle_LMU