Missing matrix/data in API call with multiple siteIds

I’m experiencing some inconsistencies requesting data from my Matomo database.
When requesting VisitsSummary.get data from 2 siteIds I get a Json response with empty data, but not when using single siteId in the request.

I’m using Matomo 4.14.1
Is this a bug or am I doing something wrong?

Response with “idSite=1”:
Url: /index.php?module=API&method=VisitsSummary.get&idSite=1&period=range&date=2021-03-22,2022-03-22&format=JSON&token_auth=Redacted
Result: {“nb_visits”:0,“nb_actions”:0,“nb_visits_converted”:0,“bounce_count”:0,“sum_visit_length”:0,“max_actions”:0,“bounce_rate”:“0%”,“nb_actions_per_visit”:0,“avg_time_on_site”:0}

Response with “idSite=2”:
Url: /index.php?module=API&method=VisitsSummary.get&idSite=2&period=range&date=2021-03-22,2022-03-22&format=JSON&token_auth=Redacted
Result: {“nb_visits”:0,“nb_actions”:0,“nb_visits_converted”:0,“bounce_count”:0,“sum_visit_length”:0,“max_actions”:0,“bounce_rate”:“0%”,“nb_actions_per_visit”:0,“avg_time_on_site”:0}

Response with “idSite=1,2”:
Url: /index.php?module=API&method=VisitsSummary.get&idSite=1,2&period=range&date=2021-03-22,2022-03-22&format=JSON&token_auth=Redacted
Result: {“1”:[],“2”:[]}

I can also get almost the same error when using the demo from the documentation.

Url: https://demo.matomo.cloud/?module=API&method=VisitsSummary.get&idSite=1,2&period=day&date=yesterday&format=JSON&token_auth=anonymous
Result: {“1”:{“nb_uniq_visitors”:2838,“nb_users”:1,“nb_visits”:3031,“nb_actions”:5049,“nb_visits_converted”:200,“bounce_count”:2092,“sum_visit_length”:406625,“max_actions”:15,“bounce_rate”:“69%”,“nb_actions_per_visit”:1.7,“avg_time_on_site”:134},“2”:[]}
See the last part “,“2”:[]}”.

Hi @Jonas82 ,
It seems this is a little bug, I invite you to create a GitHub ticket at: