An additional concern might be that if you are also performing routing with next, there might be some interference between the two (netlify’s redirect engine and next).
the best way to test that would probably be to have a little test site without next where you test your redirects syntax and see if it works properly without next. if no, then you’ll need to do a bit more troubleshooting:
if yes, then we’ll need to figure out how to make your next redirects and netlify redirects play nicely together, but lets go through the above steps first. try this and let us know?