I have never had a problem like this with importing from Altium. We use the Desktop EDA link.
Do holes come in OK? Only slots have the problem?
Perhaps it is a problem with a setting in the Altium export.
The holes come in OK. It is the slots and sometimes the radius on the edges of the board. I have been tring to get in touch with our Altium vender for support. I agree that it might a problem with how the slot was created in Altium or the export settings. I need to know what setting to use to pass this on to our E-CAD department.