Suddenly Fabric is complaining about wrong datatype (date) from lakehouse to warehouse

[nioj2S]

Hi!

I have several dataflow gen2 (not with git integration), that suddenly have started failing, when they have worked before. They all complain about datatypes in date columns. Error is:

WriteToDataDestination: There was a problem refreshing the dataflow: 'Couldn't refresh the entity because of an issue with the mashup document MashupException.Error: Expression.Error: We can't update the table. The type of column 'dateColumn' doesn't match the type of the column in the table. Details: Reason = Expression.Error;ErrorCode = 10557;Microsoft.Data.Mashup.Error.Context = User'. Error code: Mashup Exception Expression Error

We have not changed any target tables, the dataflow has run previously without issues. We first got this issue on a dataflow last week and solved it by dropping the target table and recreating it, and now we have the same issue on two dataflows (so far). It is on dataflows that copy data from a lakehouse to a warehouse. I found another thread mentioning that the staging warehouse/lakehouse changes date to datetime and then when the target table in warehouse has date, it gives error. But it has worked previously? Why stop working now? See screenshot (ignore red lines, they failed due to other reasons.)

Please advice, it isn't reasonable for us to drop all target tables and recreate them.

[v-priyankata]

Hi @nioj2S 
We regret the inconvenience caused and acknowledge your requirements. as suggested by @lbendlin  Please consider raising a Microsoft support ticket for further investigation. You can explain all the troubleshooting steps you have taken to help them better understand the issue.

You can create a Microsoft support ticket with the help of the link below:
How to create a Fabric and Power BI Support ticket - Power BI | Microsoft Learn

If this helps, please accept it as a solution and drop a "Kudos" so other members can find it more easily.

Thank you.

[nioj2S · Accepted solution]

Hi! I did raise a ticket and got this answer (in March 2025) after a couple of back-and-forths:

"We would like to inform you that we have received an update from our product team. The issue you reported has been identified as a bug in the backend, and our product team is currently working on the fix. In the meantime, they have provided a workaround: export the PQT file of the failed dataflow, create a new dataflow, import the template, and reset the output destinations."

[HimanshuS-msft]

Facing the same issue on my side also .

[RasmusK]

I have excatly the same issue.
Broke like a week ago and I fixed it by recreating the entire DataFlow Gen2.
Now suddently I it breaks down again on all tables containing a date. Other tables works fine.

So frustrating

[nioj2S]

Yeah, noticed that deleting the dataflow and recreating it worked. Could at least use the "Export template" as a base, but still annoying having to redo all the data destinations and mappings.

Also had another date related issue yesterday, where date filtering suddenly stopped working. Just had to remove that step in the power query steps and redo it exactly the same, then it started working. And my colleague had issues with locales suddenly stopped working, so he had to redo those steps. Fabric is introducing way too many new bugs at the moment...

[lbendlin]

If you have a Pro license you can open a Pro ticket at https://admin.powerplatform.microsoft.com/newsupportticket/powerbi
Otherwise you can raise an issue at https://community.fabric.microsoft.com/t5/Issues/idb-p/Issues .