
Yes, I’ve seen this before. Subgrids don’t always open the form you expect. When you click a record from a subgrid, Dataverse opens the first available main form based on Form Order and security role access, not necessarily the form you think is the default.
Please check the Main Form Order for the child entity and make sure your intended main form is at the top. Also verify that users have access to that form through their security roles. Once the form order and security role are corrected, the subgrid will open the correct main form.
Reference:
https://learn.microsoft.com/en-us/power-apps/maker/model-driven-apps/form-order