Trace plots show odd results with some versions of lmfit and emcee

[boivinalex]

Trace plots appear to "resonate" with some versions of both lmfit and emcee.

No problem with emcee 3.0.2 and lmfit 9.14.

Combinations that have been tested and do not work:

emcee 3.0rc2 with lmfit 9.15, lmfit 9.15rc1, lmfit 1.0.0, lmfit 1.0.1
emcee 3.0rc2 and lmfit 9.14 fails to plot with settings that work for other versions.
emcee 3.0.2 and lmfit 9.15, lmfit 9.15rc1, lmfit 1.0.0, lmfit 1.0.1

Possible problem with the way lmfit handles model parameters after 0.9.14?