Thanks to Daniel Schilperoord (Mendix) we have a temporary solution. We've added following code in our theming, right below the include of mendix.js / mxui.js:
By adding this code the focus will be set on the button at the moment that you click on the button. Seems like IE8 doesn't always recognize a change in a input field and therefore not send it to the server. By losing the focus in the input field, we force the client to send all changes in the form to the Mendix server.
We will update our ticket in the support portal with a testproject so that Mendix can fix this in the mendix framwork.
We've had a similar problem, where users would enter data in a form and although the data had been entered, a microflow which checked the data considered these fields empty. This problem only occured in IE8.
This is indeed a bug, which has already been reported by Samet Kaya. The bug was caused by Internet Explorer 8 not moving the focus to the button once clicked. A change to an input field is only handled once it loses the focus. If it does not lose the focus the change will not be sent to the runtime before executing the save action.
This bug will be fixed in the next maintenance release. In the meanwhile the workaround suggested by Samet can safely be used. The snippet suggested by Rom van Arendonk fixed another problem with Internet Explorer, where an input field didn't get the focus at all while it was still possible to enter text. Although the result was the same (values were not saved) this has already been fixed in version 3.3.0 (so it should be removed to avoid unexpected behavior).
I've checked the theme for my project, and found .js file which was used. This is the code:
removed to avoid confusion: this bug has been fixed in 3.3.0, see comments.