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Formula.Firewall - Please rebuild this combination error

Hi all,


Seeking your assistance on understanding this error.  I've read some of the blogs on the error but it doesn't quite make sense to me.


I get this error in a large number of my queries whenever I change a parameter in my PowerBI model to reference a new file.  The bit that confuses is me is that the error only occurs on the last step of my queries (often that step is to change the data type), and can be rectified by simply modifying the step in anyway and re-instating it exactly as it was before.  The error then disappears.


This tells me that the system is perfectly capable of processing my queries but seems to get 'hung up' on the fact I modify a parameter.


Hoping someone could help me understand why the system creates an error when its perfectly capable of processes the query?


Thanks in advance!

Community Support Team
Community Support Team

Re: Formula.Firewall - Please rebuild this combination error

Hi @KCinMelbourne


Have you read this bolg which helped some one had the similar error with yours?


If you still need help, could you show the screenshots of the error message?


I would appreciate it if you could share the dummy sample of your M Query in Advanced Editor.


Best Regards,


Community Support Team _ Cherry Gao
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

Re: Formula.Firewall - Please rebuild this combination error

Hi Cherry (@v-piga-msft),


I had tried that blog on researching this previously.  Here is an example of one my tables that has corrupted on refresh last night despite not having changed any of my parameters.


Error 1 - Formula Firewall.PNG


You'll note that this is referencing a SharePoint file and does not otherwise merge, unless invoking a function causes the same error. This would be a woeful design though considering that invoked function is system generated when you extract data from the file. 


Following is the code for reference. 


    Source = SharePoint.Files(P_SharePointLocation, [ApiVersion = 15]),
    Custom1 = Table.SelectRows(Source, each Text.StartsWith([Folder Path], P_SharePointProjFcstSubmissions) or Text.StartsWith([Folder Path], P_SharePointProjBudSubmissions)),
    #"Invoke Custom Function1" = Table.AddColumn(Custom1, "Transform File from Query1 (4)", each #"Transform File from Query1 (4)"([Content])),
    #"Renamed Columns1" = Table.RenameColumns(#"Invoke Custom Function1", {"Name", "Source.Name"}),
    #"Removed Other Columns1" = Table.SelectColumns(#"Renamed Columns1", {"Source.Name", "Transform File from Query1 (4)"}),
    #"Expanded Table Column1" = Table.ExpandTableColumn(#"Removed Other Columns1", "Transform File from Query1 (4)", Table.ColumnNames(#"Transform File from Query1 (4)"(#"Sample File (4)"))),
    #"Trimmed Text" = Table.TransformColumns(#"Expanded Table Column1",{{"Resource Name or <new demand>", Text.Trim, type text}}),
    #"Replaced Value" = Table.ReplaceValue(#"Trimmed Text",null,0,Replacer.ReplaceValue,{"FTE #(lf)Jan-18", "FTE #(lf)Feb-18", "FTE #(lf)Mar-18", "FTE #(lf)Apr-18", "FTE #(lf)May-18", "FTE #(lf)Jun-18", "FTE #(lf)Jul-18", "FTE #(lf)Aug-18", "FTE #(lf)Sep-18", "FTE #(lf)Oct-18", "FTE #(lf)Nov-18", "FTE #(lf)Dec-18", "Total Days 2018", "FTE #(lf)Jan-19", "FTE #(lf)Feb-19", "FTE #(lf)Mar-19", "FTE #(lf)Apr-19", "FTE #(lf)May-19", "FTE #(lf)Jun-19", "FTE #(lf)Jul-19", "FTE #(lf)Aug-19", "FTE #(lf)Sep-19", "FTE #(lf)Oct-19", "FTE #(lf)Nov-19", "FTE #(lf)Dec-19", "Total Days 2019", "FTE#(lf)2020", "FTE#(lf)2021", "FTE#(lf)2022", "Total Days WoL"})
    #"Replaced Value"

Any alternate suggestions would be very welcome.



Re: Formula.Firewall - Please rebuild this combination error

Hi @v-piga-msft,


Just touching base to see if you might have been able to find any alternate troubleshooting options for this issue.