Issue #1 - Failing to load, redirect loop
According to your comments about the error logs the product page is doing a redirect to itself, and getting stuck in that loop. This explains the "10 internal redirects" error message. The access log error is likely just a side effect of having so many of the same repeat requests in such a brief time window.
Note that I could not reproduce this issue, but I got a very similar issue (below). I was unable to determine why this is happening through poking around. This may take some code investigation (aka, on your end). Is this a custom WP theme?
Issue #2 - Loading complete, but not displayed
A second type of error occurs which is similar. Middle-click or open a product in a new tab. Or click on a direct link to a product, such as: http://museiam.ca/product/black-cut-sleeve-sweater/
The content will load, but it will be a white page. In this case, the javascript has loaded content but did not complete the loading event to make it visible.
You can confirm the second issue by opening your dev tools (for chrome: F12), and entering the following javascript into the script console:
jQuery('.global_content_wrapper').css('opacity', 1)
This should make the content visible.
EDIT: It seems issue #2 is also inconsistent, sometimes it does work - though much less often than following a link from within the website. These two issues may be one in the same.