Blurred DOF area of foreground elements is warping the background.
Click arrows to step through frames.
Houdini 12.0.626 on Linux
Camera "Sampling" with "radial" or "box" Bokeh gives a similar result.
Mantra Surface Shader applied to yellow spheres without any
SSS, object reflection, refraction, emmission, transparency, or displacement.
Motion blur disabled. DOF enabled.
All Mantra render engines give a similar result.