Bot runs whilst watching but fails unattended

We have a bot which signs onto our ERP system and uses a Supplier Metrics screen for a list of suppliers to create a scorecard and email it.

If I watch the bot run on an unattended machine, it works fine.

If i submit is without logging on to the unattended machine,, it fails.

The line it fails on is to clear the Supplier code field. Therefore, when it searches, it returns the information from the first supplier for all subsequent suppliers.

I have tried using backspace, delete and a backspace-home-shit-end-delete combo. All do the same, work if I watch it, fail if I don’t.  Any ideas? I can’t see why it fails as it works if I watch it.