That's because you're using the index I believe. Now, is everything working fine?
Support Forum
Hey kamran812,
You shouldn't use data
as it's an internal property (you won't see it available in the public API here https://bryntum.com/products/grid/docs/api/Core/data/Model)
We recommend using the https://bryntum.com/products/grid/docs/api/Core/data/Model#function-set function
grid.store.getAt(i).set("id", updateModifiedRowsReturn[j].sub_job_id);
Best regards,
Márcio