scheduled refresh COM error: mscorlib, An element with the same key has already been added

[Anonymous]

I have several reports on power bi report server which were regularly refreshing every hour. Even since I updated my PowerBI Desktop and Report Server to October 2020, some of these reports are not refreshing and the message I receive is this: 

"COM error: mscorlib, An element with the same key has already been added"

I checked everything, like column names with the same name, duplicates, etc. but everything is fine. I can refresh the report without any problem on the Desktop, but the schedule refresh is not running. 

Can anyone help? 
I am running out of ideas

[Anonymous]

Are there any updates on this topic? I REALLY need a solution to this like yesterday! Until one is found, I am stuck waking up at 6 AM EVERY day to download, refresh, and republish dashboards that were created solely for their ability to automate manual data compilation. This seems like yet another major Microsoft oversight with PBRS.

[RadimB · Accepted solution]

@Anonymous there is a workaround posted by MS at the bottom of this thread: https://community.powerbi.com/t5/Report-Server/December-2020-Update-Issues-Regarding-Power-BI-Report-Server/td-p/1560294

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How to Disable Enhanced Dataset Metadata

Note that Desktop authors can control if the enhanced metadata format is used when editing reports. If you are experiencing the above or similar errors, we recommend disabling the options in desktop as follows:

1. Turn off the Enhanced Dataset Metadata option in Power BI Desktop RS
   1.  In Options, under Preview Features, uncheck “Store datasets using enhanced metadata format”
2. Restart Power BI Desktop for Report Server
3. Restore the old report from the hidden backup in AppData.
   1. Before the file is upgraded to the new format, a backup copy is saved in the app data folder. For example: C:\Users\myuser\AppData\Local\Microsoft\Power BI Desktop SSRS\TempSaves\Backups.
   2. Open the backup and you should be able to save the old version of the report back to the server.

The automatic refresh works again for me after restoring the backed-up version.

[daxman]

This doesn't work for me because I'm on PBI Report Server (October 2020), which doesn't have any Preview setting options available.

[Anonymous]

You will find the Preview features in the PBI desktop client settings, i.e., not in PBIRS itself. (The preview features have been around for a long time.) I think you will fins it there unless There is something I did not understand in your post. 😉

[daxman]

Update: the January 2021 version of Power BI Report Server (and the associated Desktop tool) have resolved this issue for me. The bug seems to have been patched.

[Anonymous]

Thank you @RadimB it worked for me !!!!
🎆

[Anonymous]

Hi,

We have the same issues. It only affect the existing reports we start editing in the new version and somehow seems linked to the merge operation in M query. I will come back with details if/when I identify the problem at our end.

[RadimB]

I have the exact same problem. I'm getting this error ever since we upgraded RS to Oct 2020. The refresh worked fine before the update, there are no duplicates etc.

Only workaround now is to refresh on the Desktop (because it still works there) and upload to RS, which is a terrible solution.

So maybe there is a bug in the release?

[Anonymous]

@RadimB yes, as far as I understood this is a bug. We are no the only ones experiencing this issue