If you receive the error "Uncaught SyntaxError: Unexpected token O in JSON at position 145" on the product detail page, and the product image is no longer loaded and no AJAX / JavaScript operations work anymore, the solution may be relatively simple. In our online store running Magento 2 (Magento CE 2.2.5), the product name contained the "inch symbol" (") in the form of a double quotation mark.
We replaced this double quotation mark with two single quotation marks, and everything worked again. Hope it helps! :-)
