printing dot percentages below 20%

hi, we are running 2 Komoris, one is the LS 540, a 5 colour with coating which
we run using alcohol in the water. the second machine is a K440 p perfector
which we run as an alcohol free press. We are happy with our colour
curve tests for which we use Pressign 2, although outdated it still gives a good
indication of how the presses are printing and we are happy with the results. The
problem we have is that we will get a score of 94% to 97% which is great,but then
when we measure the 2%, 5% and up to 20% dots using a techkondens those percentages
show readings which are out of tolerance ie;2% would have a 7% and a 5% would
read as 12%. All the dots above 20% on both presses are good and within tolerance.
Any ideas on why we are getting such a gain on the lower percentages on the print?
We use Agfa P970 Thermostar plates and the processor is a PTR8800, when reading
the dots on the Linear plates they read true to what they should be, but once
on the press we get that gain on the lower percentages. HELP!!!!!!!