Looping over subreports

I am using VS 2019 and Crystal Reports SP31. I am trying to set the logon information for several subreports.

I have statement that loops over the subreports as follows:

Dim sbr As CrystalDecisions.CrystalReports.Engine.ReportDocument

For Each sbr In crpt.Subreports

crpt is a Crystal Reports document with subreports.

When the second statement is executed, the system is very very slow to complete. Up to a minute. What could cause this issue?