You'll need to provide more information to get help on this. Best I can tell, this error message originates here: https://github.com/dato-code/SFrame/blob/master/oss_src/sframe/sarray.hpp#L774
So this is when an SArray is being written. Perhaps whatever type that we are attempting to write has a string representation that looks like an integer, hence the confusing error message. Can you give us some Python code that returns this error message? Then maybe we can figure out if there's a bug or a more helpful error message is in order.