I mocked up an example addIn that exhibits the same behaviour. Unfortuantely I can't upload it from my work PC but it's very simple:
The ribbon XML is:
<customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui">
<ribbon startFromScratch="false">
<tabs>
<tab id="Example" label="Example">
<group id="Test" label="Test" imageMso="FileNew">
<box id="TestBox1" boxStyle="vertical">
<button id="TestButton" imageMso="HappyFace" size="normal" screentip="A screentip" supertip="A supertip"/>
</box>
</group>
</tab>
</tabs>
</ribbon>
</customUI>
The VBA is in a single module and consists of:
Option Explicit
Sub Test()
'Empty subroutine to allow saving as a .pptm
End Sub