Do you always carefully read every document on your ancestor for potential clues regarding alternate spellings or pronunciations of the name?
The Declaration of Intent for John Schleicher lists his name as John Sliger in one location on the declaration, with "Sliger" crossed out and "Schleicher" written above it. Everywhere else on the document the spelling of Schleicher is used. If I was unaware of how German names were pronounced, the Sliger spelling would have helped me as that's likely very close to how John actually said his name.
And of course, that spelling may be used in census and other records.