Hi Javier,
Greetings from Syncfusion Support.
Based on your query we suspect that you are facing an expand/collapse issue in the detailTemplate of the Grid. So we have prepared a sample based on your code example but we did not face the mentioned issue at our end.
For your convenience we have attached the sample and please find the sample for your reference
1) Share your complete Grid rendering code.
2) If possible please replicate the issue in the attached sample.
3) Syncfusion package version
Regards,
Shalini M.