I’ve had some trouble with toggling latex fragment previews in a document on OS X. It would sometimes work, sometimes not, so I could just try a few times until it worked and get on with things. Looking into it more, the problem seems to be with the HFS+ filesystem’s second granularity on file timestamps. The Org code checks that the generated file is not older than a (current-time) obtained before starting latex compilation, but the truncated time of the generated file can indeed be older in the sub-second fields of the timestamp.

The attached patch simply compares timestamps truncated to 1-second precision. This does mean that there is the possibility of a false positive in the compilation test if a successful compilation is followed up by an unsuccessful compilation in less than one second. I do not know if anyone encounters such a scenario.

Anthony