Super Bias yielding vertical Lines

[straittalk1947]

I'm a newbie to PI.  When I produce a super bias from an integrated bias from 40 frames, the process produces a dense frame of vertical lines.  The integrated bias and super bias can be seen here: https://www.dropbox.com/s/vey0fgv4lorq6s2/Bias.gif?dl=0.  Where are the vertical lines coming from?  Thanks in advance.

[pfile]

that's what a superbias looks like - the idea is that all the noise has been removed and you are left with the pure bias values.

rob