Using the 7.x Demo page on your site - choose editors and validations.
In the table click on an order date cell. The date picker will popup. Choose a new date by clicking on a date. The datepicker will close and the date in the cell remains unchanged. You can repeat this on other order date cells.
However, if you click on another cell (for example a dropdown cell) and then click on an order date cell and choose a date, the new date will populate.
So the problem in your demos only happens if you have not opened other editors on the grid besides the datepicker editors.
We were seeing this in our application as soon as we updated to 7.6. Version 7.5 worked fine. So I tried it in your demo page and the behavior was the same. Your 6.x demos work fine. In our application clicking on another cell does not clear the issue, so there is something slightly different there. But since it can easily be reproduced in the demo page it is obviously a regression from 7.5 to 7.6.
This is prohibiting us from upgrading to 7.6 for other features we need (like Manual sizing of textarea editors).
Thank you