Mike,
You can see what options are selected for a Notebook by getting a handle to the Notebook and running the Options] command. See my post answering a nearly identical [Question. By doing `Options[Notebooks[][1]]
(Assuming that your Notebook is the first one in the list) I get:
{FrontEndVersion ->
"11.0 for Mac OS X x86 (32-bit, 64-bit Kernel) (September 21, \
2016)", ScreenStyleEnvironment -> "Working",
StyleDefinitions ->
Notebook[{Cell[
StyleData[
StyleDefinitions ->
FrontEnd`FileName[{"SlideShow"}, "Water.nb",
CharacterEncoding -> "UTF-8"]]],
Cell[StyleData["Title", "SlideShow"], FontFamily -> "Helvetica",
FontSize -> 68, FontWeight -> "Bold", FontSlant -> "Plain",
FontVariations -> {"StrikeThrough" -> False,
"Underline" -> False}],
Cell[StyleData["Section", "SlideShow"], FontFamily -> "Helvetica",
FontSize -> 44, FontWeight -> "Bold", FontSlant -> "Plain",
FontVariations -> {"StrikeThrough" -> False,
"Underline" -> False}],
Cell[StyleData["Subsection", "SlideShow"],
FontFamily -> "Helvetica", FontSize -> 38, FontWeight -> "Bold",
FontSlant -> "Plain",
FontVariations -> {"StrikeThrough" -> False,
"Underline" -> False}],
Cell[StyleData["Subsubsection", "SlideShow"],
FontFamily -> "Helvetica", FontSize -> 28, FontWeight -> "Bold",
FontSlant -> "Plain",
FontVariations -> {"StrikeThrough" -> False,
"Underline" -> False}]}, Visible -> False,
FrontEndVersion ->
"11.0 for Mac OS X x86 (32-bit, 64-bit Kernel) (September 21, \
2016)", StyleDefinitions -> "PrivateStylesheetFormatting.nb"],
TaggingRules -> {"SlideShow" -> True,
"SlideshowSettings" -> {"WindowElements" -> {"MagnificationPopUp",
"HorizontalScrollBar", "StatusArea", "VerticalScrollBar"}}},
WindowMargins -> {{245, Automatic}, {Automatic, 22}},
WindowSize -> {1280, 960}}
When I open your notebook, I do not see a problem (or at least I am not understanding what problem you are observing because your image did not get posted) so I am guessing that the problem is in a stylesheet that I do not have. I see that you rely on a stylesheet called PrivateStylesheetFormatting.nb. Your problem may be in there. You should be able to isolate the problematic option by doing the sequence detailed in the other post referenced above. If the problem really is in this notebook, you should go through the options listed above and narrow down which one is unwanted.
Regards