Are you referring to 'transcriptions" saying they were married in both 1783 and 1784 and where have you seen these ?
The images for the BTs are available on Family Search (you need to sign in with a free account). They are not searchable but you can browse through the images. They can be confusing as, given the physical size of the original document, they have often been filmed as partial pages. So one area of a page can be on more than one image. If that makes sense.
Start here:
https://www.familysearch.org/search/collection/1309819Navigate from there to the images for St John Newcastle for the time period you are interested in. For the period 1748-1804 there are 385 images in the dataset.
This is the page that has the heading to say these were events which took place between 25th March 1783 and 25th March 1784. (its image 107 of 385)
https://www.familysearch.org/ark:/61903/3:1:S3HY-6SSF-TK?i=106&wc=9K53-6TL%3A13617901%2C28552501%2C28552502&cc=1309819Nov 1783 is included on that page and William and Ann are recorded as being married on 8th November
1783. From that page the transcriber has, correctly, entered it as taking place in 1783.
There is another image (image 109 of 385)) that also shows a marriage on Nov 8th for these people
https://www.familysearch.org/ark:/61903/3:1:S3HY-6SSN-7V?i=108&wc=9K53-6TL%3A13617901%2C28552501%2C28552502&cc=1309819 BUT if you compare that to the first image (the one that shows the date) you'll see that its a partial image of the same page - but has no year showing as its only a partial image of the document.
I'd say there's a good chance that whoever has transcribed these has not realised that the second one is a duplication and has assumed its the following year and has transcribed it as different marriage dated 1784
To see the original Parish Registers, Tyne and Wear Archives will have them on microfilm, Woodhorn hold the originals (and will have both microfilm and digital images) or, if you can visit an LDS Family History Centre, you should be able to see the digital images on their computers.
Boo