Deployment failing at validation template

[efizdxl]

Validating template...
Warning: ERROR: 'str' object has no attribute 'get'

Warning: Template validation failed.
Creating deployment...
Error: ERROR: 'str' object has no attribute 'get'

Error: Deployment failed.

[leolgrd]

Facing the same error here on a standard deployment that used to work properly.

Logs from the run:

Run azure/arm-deploy@v1
  with:
    resourceGroupName: *****
    template: ARMTemplateForFactory.json
    parameters: .github/config/ARMTemplateParameters_prod.json factoryName=******
    failOnStdErr: true
  
Validating template...
Warning: ERROR: 'str' object has no attribute 'get'

Warning: Template validation failed.
Creating deployment...
##[debug]exec tool: /usr/bin/az
##[debug]arguments:
##[debug]   deployment
##[debug]   group
##[debug]   create
##[debug]   --resource-group
##[debug]   *****
##[debug]   --template-file
##[debug]   ARMTemplateForFactory.json
##[debug]   --mode
##[debug]   Incremental
##[debug]   --parameters
##[debug]   .github/config/ARMTemplateParameters_prod.json
##[debug]   factoryName=******
##[debug]   -o
##[debug]   json
Error: ERROR: 'str' object has no attribute 'get'

##[debug]Exit code 1 received from tool '/usr/bin/az'
##[debug]STDIO streams have closed for tool '/usr/bin/az'
Error: Deployment failed.