Composite model. Measures do not IGNORE format strings measures from underlaying models.

[Anonymous]

A typical query from a visual adds IGNORE around default format string measures. If a measure is from a composite model, the composite model will translate the query and send it to the underlaying model. The translated query will NOT have the IGNORE  instruction. That leads to a cartesian product of all attributes sent from the underlying model to the composite one. 

It is super slow and inefficient. There is a workaround: create a measure referencing the underlying measure but that eliminates the whole idea of the Composite models. It does look like a bug. 

[Anonymous]

Hi  @Anonymous ,

Based on the above information, It's a reproducible issue. Due to the new reply policy, I would suggest opening a Support Ticket.

If you are a Power BI Pro or Fabric licensee, you can create a support ticket for free and a dedicated Microsoft engineer will come to solve the problem for you. 
It would be great if you continue to share in this issue to help others with similar problems after you know the root cause or solution.

The link of Power BI Support: Support | Microsoft Power BI

For how to create a support ticket, please refer to How to create a support ticket in Power BI - Microsoft Power BI Community

Best Regards,
Community Support Team _ Caitlyn