@Gerald Mull Welcome to Microsoft Q & A Community Forum. A similar question has been asked on GitHub Channel. Based on the discussion , seems due to difference in version of PowerShell and Bicep, the mentioned error is prompted. Kindly check if its the case with your issue as well.
Reference Link : https://github.com/Azure/bicep/discussions/3140
If this is not the case, kindly share below information for further analysis
- Az CLI version or PowerShell version
- Bicep version
- Template that you are trying to deploy