We were not able to reproduce any issues you have reported in your sample. After adding a job details, and by selecting that job from drop down then we can able to add, edit and delete the records successfully in the new Gantt. Can you please share us more details along with the replication procedure to reproduce issue you are facing.
Sorry about the inconvenience caused.
We were able to reproduce the issue of, all the text fields get locked after we selected the time in date time picker. Hence we have logged a feature report regarding this. A support incident has been created under your account to track the status of this requirement. Please log on to our support website to check for further updates.
Please let us know if you need further assistance on this.