Hello,
We are also experiencing this issue at our company. We just migrated from Exchange 2013 to Exchange 2019 CU9. We use Outlook in online mode. We cannot use Outlook in Cached Mode.
When you do a search in outlook it only returns the past couple of weeks then skips 4 months then returns the rest of the results.
CU 9 did not fix the search issue.
I also upgraded to Outlook 2019 from Outlook 2013 which did not fix the issue.
I tried some suggestions to move the mailbox to another database which did not work.
When you run the powershell command for big funnel everything appears to be fine.
We do not have Software Assurance so Microsoft will not speak to me.
It's funny Microsoft will take your money for a purchase but if their product is broke they will not warranty it.
Microsoft fix this issue. It is still broke.
Provide some warranty support for your product.