The Python plotting library matplotlib can cause side effects that may impact Gurobi. When creating a matplotlib figure, the locale settings may be modified by matplotlib. Along with other changes, this may lead to different decimal point characters, depending on your previous locale and region settings.
One way to avoid these side effects is to reset the locale settings after creating a figure:
import locale
locale.setlocale(locale.LC_NUMERIC, 'en_US.UTF-8')
This behavior is a known issue with matplotlib.