Query on migrated customer open items

Dear SAP We have a question regarding migrated open items. Issue1: As Migration date we have set 30.03.2020 in the Testsystem and then have migrated open items for suppliers and customers. Therefore the posting date of the migrated open items is set to 30.03.2020. We also have migrated open items with due dates in 2019 or beginning of 2020. When we now search for "Open on Key Date" = 29.03.2020 we do not find any open items. But when we set the search date on the migration date or anytime after the migration date, the open items are found. Issue 2: Our client has a process, where they look for open items for credits that are open for p.e. 6 months. When they can not clear it with another open item within this 6 month, they send the customer a letter asking them if they should transfer the money or not. In the App "Create correspondence" you encounter exactly the same situation. If you select the 29.03.2020 as "open at key date" and click on PDF preview the open item list is empty, even though there are open items that have due dates in 2019 or beginning 2020. Best Regardss.