About fanc insulation command

[GleeenSIBS]

When I use fanc insulation command to call insulation score using "-o bigwig" option, it showed the following errors:
RuntimeError: The entries you tried to add are out of order, precede already added entries, or otherwise use illegal values.
Please correct this and try again.
However, "-o bed" and "-o gff" work. My command is "fanc insulation ../../0.fanc.files/CTRL_merged_40000_iced.fanc CTRL_merged_40000_iced -w 400000 -o bigwig". So, I want to know the reason why I meet this error and how to solve it. Thanks!