Hi @TekaTeki,
Thank you for providing access. 
I’ve carefully investigated your app and here is the result:
First of all, the problem was that the selected dates were empty while we were editing the task. As you said the initial dates appear to be correct but the dates are deleted from the database because we didn’t select “new” dates when we try to edit/save them. Thus, when we save the task without any changes, we don’t see any date since it’s empty in the database.
I’ve added a new event as an example and the dates are displayed correctly. Here:
Also here is a short video for a better understanding: https://www.loom.com/share/7df2c3a3280949ceb428013ed4d4f339
In this case, you need to change the logic I’m afraid. I would like to suggest you create separate events to save task (create a new task and make changes to the task) and add this condition (Screenshot by Lightshot) to save the task with previously selected dates if no changes have been made.
Hope it helps!
Best regards,
Zeroqode Support Team