Issue provider aliases should use the IssuesAliasConstants.MainCakeAliasCategory and IssuesAliasConstants.IssueProviderCakeAliasCategory constants for defining their category:
[CakeAliasCategory(IssuesAliasConstants.MainCakeAliasCategory)]
public static class MyIssueProviderAliases
{
[CakeMethodAlias]
[CakeAliasCategory(IssuesAliasConstants.IssueProviderCakeAliasCategory)]
public static IIssueProvider MyIssueProvider(
this ICakeContext context)
{
}
}