Please be aware that the 'Fix report' function only works within a DEV-environment. This article provides a guide to resolving the following error-message 'Unable to fix non-precision design reports. Please use report replacement for such reports'

The error message would appear if a report is being fixed in an environment not containing the metadata for the report (model), like if the environment only contains AOT-packages and no models. In this scenario it's not possible to fix the report as the source-code does not exist.

The proper routine for 'Fix report'
 
  1. Start in an environment containing the source-code (models)
  2. Create a deployable package containing the model which contains the fixes - Like the model 'LACFixReportsForApplicationSuite
     The last step in the Wizard for 'Fix report' will show which model should be used to create the AOT-package
    

3.  Install or Deploy the AOT-Package into the 'next environment.
And please start using replacement reports as fix reports isn't needed with replacement reports- Performance is also much faster as there's no rendering through SSRS (reporting Server)