Could be a myriad of things, unfortunately. Have had my battery saver settings kill some background activity for example and adding Slack to the exception list

Could be a myriad of things, unfortunately. Have had my battery saver settings kill some background activity for example and adding Slack to the exception list fixed a lot of issues for me. Maybe contacting the customer experience team could help. You can just use /feedback to open a ticket and they're pretty quick to respond.