Dashboard subscriptions not working

Bug reports
1

We currently face an issue where our dashboard subscriptions arent being sent when they should be.

The subscriptions are scheduled to be sent every day at 6 am CET if there are results available.
Although there should be results to be sent, we don't receive any emails. Metabase reports that the pulse task was run successfully and the logs don't show any errors.
Subscriptions scheduled to be sent after 8 am CET (same dashboard) however work, as well as "Send email now". The only difference I noticed so far are log entries regarding the cache. The ones that are sent leave a log message
"INFO metabase.query-processor.middleware.cache Query xyz took 1.4 s to run; minimum for cache eligibility is 5.0 ms; eligible"
and those that arent say
"INFO metabase.query-processor.middleware.cache Query xyz took 1.4 s to run; minimum for cache eligibility is 5.0 ms; not eligible".
Since metabase.query-processor.middleware.cache checks if there are any rows in the result of the query it seems that the query does not get any result, which isnt correct (it checks for entries in a table on a relative date "past1day"). Re-running the Query manually confirms that there are indeed results.
We use Elastic Beanstalk to run Metabase and our database is Amazon Redshift. We tried updating metabase, deleting and recreating all subscriptions, applying recommended changes in our database structure and restarting the metabase instance.
As far as I know the problem emerged with the metabase update 0.50.19.

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    "user.language": "en",
    "user.timezone": "Europe/Berlin"
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  "metabase-info": {
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      "redshift",
      "h2"
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    "application-database": "postgres",
    "application-database-details": {
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        "name": "PostgreSQL",
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    "run-mode": "prod",
    "plan-alias": "",
    "version": {
      "date": "2024-08-13",
      "tag": "v0.50.20",
      "hash": "df82d58"
    },
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2

a few questions:

  1. if you go back to 50.19 or 50.18 this problem goes away?
  2. how do you know that there's no problem in the email gateway?
3
  1. I just checked and the problem began with 0.50.18 and before that we had version 0.48.8. We tried to downgrade back to this old version but it doesnt work anymore so that is not an option.
  2. The mailing process works fine. Emails scheduled for different times are being sent as well as "Send Email now". One thing we checked today: If we disable the option "don't send if result is empty" it works too and sends an empty result. So the query has some kind of issue that won't let it get any results although there clearly are ones.