Arestore has a condition that causes the kernel not to be shifted when the kernel's origin is at L/2, where L is the length of the data axes. For instance, if both the input image and the PSF 128x128 and the psf_x_center and psf_y_center are left at INDEF, this bug is triggered.
Trim one pixel from the PSF. This can be done with a virtual file specification in the psffile parameter:
unix% pset arestore psffile="psf.fits[#1=1:127,#2=1:127]"