Sample jumping out of the well?

[Dom Spinella]

This problem is almost certainly due to excess ethanol in the sample,
your student's assertion about completely a dry pellet notwithstanding. 
It happens to everyone at one time or another, and it always perplexes
the first time you see it. There are a couple of easy things you can do
to avoid this.  One is to wash the pellets with 100% ethanol after the
70% wash.  The water in the 70% wash helps get rid of precipitated
salts, but also decreases the volatility of the ethanol.  A quick wash
with 100% EtOh followed by a short drying period will generally
eliminate the problem.  The other thing you can do, when you see that a
sample is leaving the pipet tip and going up instead of down, is to add
a bit more glycerol to the sample. Just immerse the the pipet tip a few
mm into a bottle or tube of glycerol and then mix it with your sample in
the original tube and re-load.  That should cure the problem. Cheers.
--Dom Spinella