Complete Composites uses uppercase I instead of dotless i

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2

The XML file is from 2016. Are you using FontCreator 9.0?

<!-- Updated 23rd June 2016 for Unicode 9.0 -->

Nevertheless, it should work fine. This is the relevant code from the XML file for lowercase i grave and acute, which has not changed in the latest version:

<Composite><!-- i grave -->
<GlyphMapping>236</GlyphMapping>
	<Member id="1">
	<GlyphMapping>305</GlyphMapping>
		<UseMetrics>TRUE</UseMetrics>
	</Member>
	<Member id="2">
	<GlyphMapping>57365</GlyphMapping>
	<GlyphMapping>96</GlyphMapping>
		<Pos>Auto</Pos>
	</Member>
	</Composite>
<Composite><!-- i acute -->
<GlyphMapping>237</GlyphMapping>
	<Member id="1">
	<GlyphMapping>305</GlyphMapping>
		<UseMetrics>TRUE</UseMetrics>
	</Member>
	<Member id="2">
	<GlyphMapping>57366</GlyphMapping>
	<GlyphMapping>180</GlyphMapping>
		<Pos>Auto</Pos>
	</Member>
	</Composite>

Perhaps you used the codepoints in the Private Use Area that are intended for low profile accents for alternate forms of Capital I? Decimal codepoint 57365 etc.

See the Tutorial on Using Complete Composites

<!-- ¶¶ Low Profile Accents for Uppercase and/or Small Capitals -->
<Composite><!-- Low Profile grave -->
<GlyphMapping>57365</GlyphMapping>
	<Member id="1">
	<GlyphMapping>96</GlyphMapping>
		<UseMetrics>TRUE</UseMetrics>
	</Member>
	</Composite>
<Composite><!-- Low Profile Acute -->
<GlyphMapping>57366</GlyphMapping>
	<Member id="1">
	<GlyphMapping>180</GlyphMapping>
		<UseMetrics>TRUE</UseMetrics>
	</Member>
	</Composite>

Some fonts (e.g. Gentium) use smaller or more acute accents for uppercase glyphs. FontCreator used to rely on these codepoints to generate composites, but in more recent versions, you can remove the codepoints that you have used incorrectly, and FontCreator will then use the fallback glyphs — grave and acute — for uppercase accented glyphs.

OpenType features, such as Stylistic Alternates can use your alternative capital I by relying on the glyphnames. The codepoints are not needed.