VBA Code works by step by step, doesn't work by running

Hello.

I'm configuring and activating OpenSolver on VBA.
I have a code that sets the objective function cell and the decision variables iteratively for 30 sheets.
If I run the code, it works for the first sheet, then it displays an error saying that the decision variables must be on the active sheet.
If I place some stops at the code and run it one F8 at a time, it runs the entire code without errors.
This seems really odd, any ideas why it's happening?

Thanks for the attention.

This is the part the it highlights when displaying the error:

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I think you need to upload the file with your model and code after removing sensitive information so one can try testing a bit.

an error saying that the decision variables must be on the active sheet.

this is the way the Excel solver is set i.e. all variables must be on the active sheet but as you say and I agree it is strange that it works when you step through your code using F8.

Alf