How to reload data stored for a sever side gutenberg block in the editor

First thing that jumps out is that in:

<!-- wp:mvc/block-mvc-offer-details {"data_offer":"2426"} /-->

the data_offer value is stored as a string while it’s defined attribute type is number.

This could be why it’s stripped after reload. While select('core').getEntityRecords does return IDs as integers it’s possible that after passing that data to <SelectControl> and then receiving the selected value back by it’s onChange(event.target.value) it has lost it’s type by being in the DOM.

Try: onChange={data_offer => setAttributes({data_offer: parseInt(data_offer)})}