Investigate why stable elastic buffers in plots are marked as unstable

[hiddemoll]

In some plots the elastic buffers are all marked as stable at the end of the run, but the 'all buffers stable end of run' is still marked as false.

Also, the 'stability detector - framesize' does not look like it is 2000 ms. In the Elastic Buffer Occupancies plot we can see the buffers of 3 <-> 4 are unstable for about 1 second.