Okay, I am beginning to gain some insight here.
Here are the tail ends of your two snapshots. The earlier one on the left, the later one on the right.
PzB_pzbedit_slowdown1.JPG (Size: 498.1 KB / Downloads: 6)
Note that, in either case but especially the one on the right, we see that the code has entered the function ForcesDraw::LoadPicture(), but there is no exit.
From the times, the beginnings of each log entry, you can see where the logging has become very slow.
There does indeed seem to be a slowdown in the graphics system indicated. [edit: Actually more than slowdown, rather, a real lock-up.]
... But, I have been called to dinner!
How about you kill the pbedit session now, and we take this up again tomorrow? In the meantime, I will ponder the mystery of this.