interact with more than one figure at the same time

I am trying to use Interact.jl with PyPlot to control various figures with a single slider. The notebook I have so far is at
http://nbviewer.ipython.org/github/berceanu/topo-photon/blob/master/anc/exploratory.ipynb
However, I am facing various problems.
1.
The first one is that _sometimes_ I get the following error instead of a plot as output of the `#plot spectrum` cell. If I then re-evaluate the cell, everything gets back to normal.

```
PyError (:PyObject_Call)
AttributeError("'FontProperties' object has no attribute '_family'",)
File "/usr/lib/python3.4/site-packages/matplotlib/backend_bases.py", line 2158, in print_figure
**kwargs)
File "/usr/lib/python3.4/site-packages/matplotlib/backends/backend_agg.py", line 521, in print_png
FigureCanvasAgg.draw(self)
File "/usr/lib/python3.4/site-packages/matplotlib/backends/backend_agg.py", line 469, in draw
self.figure.draw(self.renderer)
File "/usr/lib/python3.4/site-packages/matplotlib/artist.py", line 59, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/usr/lib/python3.4/site-packages/matplotlib/figure.py", line 1017, in draw
self.tight_layout(renderer, **self._tight_parameters)
File "/usr/lib/python3.4/site-packages/matplotlib/figure.py", line 1663, in tight_layout
rect=rect)
File "/usr/lib/python3.4/site-packages/matplotlib/tight_layout.py", line 352, in get_tight_layout_figure
pad=pad, h_pad=h_pad, w_pad=w_pad)
File "/usr/lib/python3.4/site-packages/matplotlib/tight_layout.py", line 129, in auto_adjust_subplotpars
tight_bbox_raw = union([ax.get_tightbbox(renderer) for ax in subplots])
File "/usr/lib/python3.4/site-packages/matplotlib/tight_layout.py", line 129, in
tight_bbox_raw = union([ax.get_tightbbox(renderer) for ax in subplots])
File "/usr/lib/python3.4/site-packages/matplotlib/axes/_base.py", line 3276, in get_tightbbox
bb_xaxis = self.xaxis.get_tightbbox(renderer)
File "/usr/lib/python3.4/site-packages/matplotlib/axis.py", line 1082, in get_tightbbox
renderer)
File "/usr/lib/python3.4/site-packages/matplotlib/axis.py", line 1065, in _get_tick_bboxes
extent = tick.label1.get_window_extent(renderer)
File "/usr/lib/python3.4/site-packages/matplotlib/text.py", line 798, in get_window_extent
bbox, info, descent = self._get_layout(self._renderer)
File "/usr/lib/python3.4/site-packages/matplotlib/text.py", line 293, in _get_layout
key = self.get_prop_tup()
File "/usr/lib/python3.4/site-packages/matplotlib/text.py", line 743, in get_prop_tup
hash(self._fontproperties),
File "/usr/lib/python3.4/site-packages/matplotlib/font_manager.py", line 702, in __hash__
l = (tuple(self.get_family()),
File "/usr/lib/python3.4/site-packages/matplotlib/font_manager.py", line 724, in get_family
if self._family is None:

in pyerr_check at /home/berceanu/.julia/v0.3/PyCall/src/exception.jl:58
in pycall at /home/berceanu/.julia/v0.3/PyCall/src/PyCall.jl:91
in fn at /home/berceanu/.julia/v0.3/PyCall/src/conversions.jl:181
in writemime at /home/berceanu/.julia/v0.3/PyPlot/src/PyPlot.jl:222
in writemime at /home/berceanu/.julia/v0.3/Interact/src/IJulia/setup.jl:91
in base64 at base64.jl:125
in display_dict at /home/berceanu/.julia/v0.3/IJulia/src/execute_request.jl:34
```
1. the second issue I am facing is that the kernel seems to die at random intervals, for no particular reason, which I find quite frustrating.
2. sometimes an empty figure frame is drawn and mixed with the output from other code cells

Am I doing something terribly wrong in my code? The non-plotting part of the code is well tested outside of IJulia, so I know that gives no issues.