Hi @Barod,
you need to use a different path variable when configuring the Excel reader. E.g., copy the file to another location and use that path as variable. Then configure the Excel Reader. Afterwards, change your path variable back. This will cause the Excel Reader to re-calculate the spec in every loop iteration.
If there are still issues, increase or remove the limit of rows that are scanned on the Advanced Settings tab.
Best,
Simon