Unable to load trace after VI

Still, I can`t pm.load_trace()

Windows10, Corei7-8700 (3.2GHz) 
RAM : 16 GB

Python : 3.7.4
pymc3 : 3.6
arviz : 0.5.1

Installed Python and pymc3 by Anaconda, arviz by pip.

I have already tried updating to pymc3 to 3.7, re-installing python and every packages.
Updating to 3.7 caused another problem : slowing pm.traceplot() speed significantly.
It took more than 5 min to plot the result of a very simple model.

Have anyone experienced similar problems?