SSIS fails after changing Excel connection string - DTS_E_CANNOTACQUIRECONNECTIONFROMCONNECTIONMANAGER

I have designed an ETL package with SSDT to import 12 Excel sheets into my destination database. The Excel sheets are reports from another system, Iteraplan in my case. Each of the Excel reports are a snapshot of the system. There are slight changes in each of these reports, but still I have defined only one connection string to the Excel reports because, in the future, there will be more reports, and I want the connection to sources to be parametric, so that after the package is deployed, users can choose the source and the package imports data independent of me.

The structure of my ETL package is one ParentPackage, which contains more than 20 Execute Package Task, in which another child package is called. Since I am still designing, as not all reports have exactly same schema, when I change the Excel connection string and refer to another Excel report, some of the packages in the "Execute Package Task" fail.

There is no driver issue, as I have installed ACE 32 bit, Run64BitRunTime is False (I have also tried True, but still same behavior), DelayValidation is True, and my original package, which is designed based on September reports, is working well. The only problem is, whenever I change Excel connection string, there are random failures of some of the child packages with either of the following errors:

DTS_E_CANNOTACQUIRECONNECTIONFROMCONNECTIONMANAGER Error: 0xC0202009 at Parent Package: SSIS Error Code DTS_E_OLEDBERROR. An OLE DB error has occurred. Error code: 0x80004005. An OLE DB record is available. Source: "Microsoft Access Database Engine" Hresult: 0x80004005 Description: "The Microsoft Access database engine cannot open or write to the file ''. It is already opened exclusively by another user, or you need permission to view and write its data.". Error: 0xC00291EC at Get Report Date From Static but Parametric Connection, Execute SQL Task: Failed to acquire connection "Static Excel Connection". Connection may not be configured correctly or you may not have the right permissions on this connection.

After changing the connection, and rebuilding the project, I again get the same error, but sometimes for different child packages. At the moment, in order to solve this, I have to close SSDT, copy the excel report, delete it, paste it back, open the project again, rebuild it and then execute it. I don't understand why it is behaving this way but I am sure there should be a way to make it behave properly. I would really appreciate it if someone shares with me their thoughts.