Images not cross-fading with Sync on, creates gap between

Problem/Motivation

A Views Slideshow implementation, previously working as intended, now has a new set of images and doesn't work the same. They're intended to cross-fade, by using transition "fade" and option "sync" checked on. Images display and they do fade. But there is a blank display of several seconds between one fade-out and the next fade-in. The settings are as follows:
Timer Delay - 3000
Speed - 1000
Initial slide delay offset - -1000
Sync - checked on, no other options activated

I tried several different timing options, but don't see any change in the appearance of the gap.
The images are significantly larger than the original ones - 1250 x 471, 532kb.
Maybe the image data size is a problem?
Otherwise, how might this be fixed?
--Thanks--