_cached_numerical_components AttributeError

[tokamage]

I fit the same set of data with three very similar models, containing nothing more complicated than polynomial and piecewise functions. This worked fine at the beginning of this year, but even reverting back to the versions of symfit, sympy and numpy used then, one of the three models now encounters the following exception:

Python\Python36\site-packages\symfit\core\support.py in __get__(self, obj, objtype)
    281         try:
--> 282             return getattr(obj, self.cache_attr)
    283         except AttributeError:

AttributeError: 'CallableModel' object has no attribute '_cached_numerical_components'

which in turn ecounters another exception:

Python\Python36\site-packages\sympy\printing\pycode.py
in _print_known_const(self, expr)
     70
     71 def _print_known_const(self, expr):
---> 72     known = self.known_constants[expr.__class__.__name__]
     73     return self._module_format(known)
     74

KeyError: 'ComplexInfinity'

Can you give me a hint what might have changed since the begining of this year and which feature of my model might cause it to behave differently than the others?

Thanks!