This again seems to be the same case as the discussions in the other similar posts as well. So you say you perform Excel Import. I have some questions,
1. Who has access to perform this Excel Import? Does a user with "Engineer" system role have the ability to do this?
2. Does your Excel Import create/update objects of MasterData?
3. You mentioned associations being created what association are we talking about.
3. What's the security level access provided for the attributes like Project and Project_Employee_UitvoerderG? What are their data types.
Please EDIT the original post add the screen snap of your Domain model showcasing the MasterData entity if possible.
A colleague of mine experienced the same difficulties, and got this response from Mendix:
"we've had reports of similar issues from other customers. Our R&D department created a fix for that issue, which will be released with Mendix 7.17. However, without a reproducible case, we can't be 100% certain this is the exact same issue you're having, so we can't guarantee your issue will be fixed as well.
In the browser a different value: 1234567912345678800 will be shown.
Clicking the Save button will trigger an error both in browser and modeler console. The client believes the value is actually changed because of the truncation/rounding, and sends a changed value back to the application. Because the attribute is not editable, a security error is shown. Setting the attribute to writable will resolve this issue, but you might not want to do that.
As said before, without a reproducible case there's not much we can investigate. We recommend you to test your application with version 7.17, once it has been released to see if the error still occurs. If you are able to create a reproducible case in the meantime, please let us know, and we will investigate it.
With kind regards"