Tefficiency TBinomialEfficiencyFitter warning

Hello Rooters,
When I use Tefficiency class, I am getting the following warning for only some of my plots and fit line is not drawn for these plots.

Warning is as the following:

> Warning in <TBinomialEfficiencyFitter::Fit>: Abnormal termination of minimization.
> Info in <TBinomialEfficiencyFitter::result>:  chi2 -686033.278248 ndf 0

Could not figure out what is causing the issue.
Any help would be appreciated.
Thanks in advance,

Damian


_ROOT Version:6.16/00
Platform: Ubuntu/Mac
Compiler: Not Provided


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