So you set the title after making sure your Component is checked out, but you tried to sync back the changes of the content before ensuring it is checked out:

...
// sync content back to Component
newComp.Content = content.ToXml();
...
// sync metadata back to Component
newComp.Metadata = embeddedFields.ToXml();
...
if (!newComp.IsCheckedOut)
{
    newComp.CheckOut();
}
newComp.Title = "TEST-" + DateTime.Now;
newComp.Save(true);

Now if you would first check if your Component needs to be checked out before syncing back its content, then I think you will get a better result on your save. Because I expect that when you call newComp.CheckOut(); all your previous actions on newComp will be reset.

So change it into something like this:

...
if (!newComp.IsCheckedOut)
{
    newComp.CheckOut();
}
newComp.Title = "TEST-" + DateTime.Now;
newComp.Content = content.ToXml();
newComp.Metadata = embeddedFields.ToXml();
newComp.Save(true);

So you set the title after making sure your Component is checked out, but you tried to sync back the changes of the content before ensuring it is checked out:

...
// sync content back to Component
newComp.Content = content.ToXml();
...
// sync metadata back to Component
newComp.Metadata = embeddedFields.ToXml();
...
if (!newComp.IsCheckedOut)
{
    newComp.CheckOut();
}
newComp.Title = "TEST-" + DateTime.Now;
newComp.Save(true);

Now if you would first check if your Component needs to be checked out before syncing back its content, then I think you will get a better result on your save. Because I expect that when you call newComp.CheckOut(); all your previous actions on newComp will be reset.

So change it into something like this:

...
if (!newComp.IsCheckedOut)
{
    newComp.CheckOut();
}
newComp.Title = "TEST-" + DateTime.Now;
newComp.Content = content.ToXml();
newComp.Metadata = embeddedFields.ToXml();
newComp.Save(true);

Note that the line if (newComp.IsCheckedOut) newComp.CheckIn(); after calling newComp.Save(true); might undo a "permanent" lock that was set on the Component. Although that might be intentional of course.