When I first started out researching my family, I was warned of changing of spellings because of regional accents. Because the Industrial revolution caused a lot of migration in certain areas from rural areas to towns and cities, accents may not have been 100% understood. If the person recording the event was not able to spell the name, the registrar/minister would just have to make a best guess based on what he had heard. A tip I was given was to hold my nose and say the name to see how the sound may change with a more nasal accent for instance - sometimes it really does help to see how things are altered!
Cheers,
Clare