Just in case anybody might be interested, I think I know the root cause of the weird LaTeX issue that everyone seems to have trouble with.
If I had to guess, the original LaTeX issue involves the browser's cache combined with the way PF assigns file names to graphics.
I'm not certain that is the case, but suspect that it's at least something like it. Here is a more detailed scenario of what I'm suspecting:
(a) User originally hits the preview button.
(b) PF processes the LaTeX code, and creates .png graphics files of the equations. Each .png graphics file gets assigned a name and a corresponding link (something or other short of like https://www.physicsforums.com/latex_images/28/2886657-0.png" , but with a slightly different location [in a special "preview" directory] and a different file name).
(c) The image gets downloaded to user via normal http protocol and displayed on the screen
(d) The link is also cached locally on the user's machine.
(e) The user makes an edit to the equation and previews it again.
(f) PF creates a new graphic overwriting the old image, re-using the same file name.
(g) Via http protocol, browser thinks that the local cached graphic is the same graphic as the one on the server (after all, they share the same URL and file name).
(h) Cached graphic gets displayed on the browser.
(i) Only by hitting "refresh" will cause the browser to reload the server content, bypassing the cache.
A solution to this might be to change the algorithm making sure that the PF server does not recycle file names for previews. Of course, that means that more graphics files get stored on the server. So maybe a fix might also involve automatically deleting "preview" graphics files after the preview session is complete, but still not recycling file names (the index for the file names keeps incrementing, even if the files are deleted).