Need to remove trailing slash which has suddenly appeared

I’ve researched this topic without finding resolution – including going to the post on canonical changes with WordPress 2.3 and trying the disable-canonical-redirects plugin with no success. Our site suddenly started adding trailing slash to all url’s without any changes that I can think of on our part. To verify this, I checked the search engine listings and they all show the url’s with no trailing slash as would be expected since that’s the way it was until very recently. We noticed the problem because when a new Page was added it was getting a 404 error.

This results in our site having to be re-indexed (which is not huge since all but the newest page automatically redirects) but it just plain doesn’t look right. For instance, I have the url for posts set up as /%postname%.html, so this now shows as https://www.sitename.com/post-name.html/ – which obviously doesn’t make sense. I also may have to do a manual redirect with each new Page as I did with the most recently added.

Any suggestions on why this may have changed or, more importantly, how to change it back? Though I don’t prefer to list the actual url, I can if necessary for resolution.

We were at 2.6.2 when the change was noticed and I upgraded to 2.6.3 with no change.

Thank you so much for any suggestions.

Christy