Odd back button behavior in Firefox

I'm having odd behavior with Mozilla Firefox's back button while viewing
Xymon tests.  This started somewhat recently but I don't recall when I
first noticed it.

Navigating to the test page is fine.  If I view the test then immediately
use the back button, Firefox goes back to the page/subpage.  If I stay on
the page for subsequent refreshes, I have to hit the back button once per
refresh that happens.  If I stay on the page long enough, the back button
history fills and I can no longer use the back button to get to the
page/subpage.

Xymon server is v 4.3.17.

I still need to test what other browsers and Firefox on a different PC are
doing in this situation.

Is anyone else having a similar experience?  Any thoughts?

Thanks.

Robert Herron
user-8b27ea4290da@xymon.invalid