Random date stamps

I teach a class of students that maintain roughly a dozen websites for our
school. It's important to show when a site has been updated, so I've had each
of my students insert on the bottom of each of their sites a date stamp that
automatically updates on save (we all use DW8). However, recently we've
noticed that some of our sites are showing a random placement of the date stamp
within individual pages (nowhere near the original date), or three or four
instances of the date right next to the date (without updating).

I've searched on this forum and found several other instances of people having
this problem (mainly in MX), but there appears to be no cause or resolution
(the posts were dated nearly a year ago). Any new ideas? We literally have to
edit the code to erase these random insertions. Is there a workaround, or do
we need to just manually type in the date that we've updated? Please note
that some of these sites use a style sheet with the date, some do not -- the
outcome is the same; some pages within the site are affected, and some are not.

Thanks.