A preprint is a citable scientific document, thus it cannot be edited or revised after being listed online. Additionally, JMIR preprints may be currently in review. Thus, they are "frozen" and cannot be changed. Authors can change title, abstract, and authors in the next revision and the final manuscript, but a posted preprint can only be annotated (see How to use the Hypothes.is annotation tool).
If authors spot errors in the metadata, it is critical to make these changes in the metadata form so they show up correctly in the "accepted manuscript" and on PubMed (if you use PubMed Now!).