Implementation of feature #1186638 leads to a race condition. In order to reproduce this bug:
The above sequence reproduces, with a long time scale, what would happen if yap is monitoring the dvi file while the dvi file is being generated. Avoiding this race condition implies mutexes of some sort (e.g. locking the dvi file) or copying the dvi file to a temporary location. Since all of them are less than optimal, I advice this feature should be removed and replaced by a method to call forced refresh from the external application (I think a simple reopening of the file suffices if the last viewed position is kept).