Many site issues can be caused by corrupt cookies or cache.

• Clear the Cache and

• Remove Cookies
  Warning ! ! This will log you out of sites you're logged in to.

Type about:preferences<Enter> in the address bar.

• Cookies; Select Privacy. Under History, select Firefox will Use Custom Settings. Press the button on the right side called Show Cookies. Use the search bar to look for the site. Note; There may be more than one entry. Remove All of them.
• Cache; Select Advanced > Network. Across from Cached Web Content, Press Clear Now.

If there is still a problem, Start Firefox in Safe Mode {web link} While you are in safe mode;

Type about:preferences#advanced<Enter> in the address bar.

Under Advanced, Select General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?

Then restart.

I tried your first suggestion but this did not resolve the problem with display for news items. I was unable to find how to start in "Safe Mode" but feel that will be equally unsuccessful.

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox. Is the problem still there?

FredMcD said

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox. Is the problem still there?

I did as you said. The first attempt with your firs suggestion yielded some display being shown Intermittently. That, although it yielded some display it was inconsistent when scrolling through the news articles. My second attempt with your second suggestion yielded display only on any news article after the first selection 1-5. When you scroll past those the displays come up but never for the first five when you scroll past the last article. It is a mystery!

If you have Avast then try to disable HTTPS scanning in Avast Web Shield.

• http://www.ghacks.net/2014/10/31/avasts-https-scanning-interferes-with-firefox-and-other-programs/