The following code in QEglFSCompositor::render does not correctly map a rectangle onto the -1 to +1 range. The right-hand x value is not width, but width-1 - this results in an upper value slightly smaller than 1. In turn, this can causes texture sampling errors near the center of the screen since nearest sampling is being employed.
I have tested the following fix which works well:
The problem was very noticeable when a full screen of small text was being displayed at 1920x1080 or 1280x720. A vertical and horizontal line of sampling artifacts (showing as smudged text) was visible through the center of the screen.