Whats the difference between these chess tempo databases Chesstempo seems to have two pages for database display.

This one works at random: https://chesstempo.com/game-database.html

Sometimes it shows the moves in sequence of most usage and then the probability of WDL.  Other times it shows nothing. 

This one seems to work all the time: https://old.chesstempo.com/game-database.html

What is the difference between the two databases?

Does that 'old.' refer to the database or to old code to display the database?

It seems to me that the 'old' UI works right and the new one is full of bugs.  Or is there some other features I am missing.  Still need an answer to the related question here.
They are currently exactly the same.

Typically, when a website does the old.sitename.com, it is to allow people to temporarily use the old format of a recently-updated website. Over time, they phase out the old one in most cases. The underlying data, such as a database, does not change at all during this transition, just the aesthetics and layout of the webpage.

In this case, it looks like they already phased out the old version, but simply kept the URL for convenience: They are currently exactly the same. To prove this, I did the following:

I opened each page in Firefox (but you could use any web browser), and right-clicked the page, and selected "View Page Source", which shows you all of the data that is used to render the webpage. I selected all the text for each document, and pasted it into a Word document. It was of note that viewing the page source, each one had 2576 lines...exactly the same. Once in Word, each document had 54 pages, and exactly 6017 words.

I then took both documents, "Old" and "New", and used the site copyleaks.com to compare them. As you can see from the screenshot, as I expected from the previous data I mentioned above, they are exactly the same.