There are a string of crashes that are occurring with UMG as the cause of the crash. This occurs when the project is upgraded from 4.16 to 4.17. With the project provided making any change to the BP that is causing the crash resolves the issue (Such as using refresh all nodes, adding a new component, or changing any value). The cause of the crash is still unknown.
4.17.P3 - CL: 3552910
Head over to the existingAnswerHub thread and let us know what's up.