When you create a package window you can only create a window time with HH:MM. Endevor is using HH:MM:SS to determine what the start time and to time are. The package can only execute in the above example between the times of 10:00:00 and 12:45:00.
When the package is set to run (from a job scheduler or submitted) and the actual time is 12:45:00,
the package is not available to be executed. Endevor uses the SS to make sure that the execution is between the
from and to date / time.
A workaround would be to add 5 minutes to the end time of the package (12:50:00) window so the package will not be outside the execution window.
If sweep jobs are run every quarter hour the package would still be in the window and will then run.