VMC Optimization Error "Safeguard failure: checkConfigurations variance out of [0.5, 2.0]"

[kyuuuuan]

Describe the bug
During VMC optimization for the quintet and triplet states of Fe²⁺ ions, I encounter the error"Safeguard failure: checkConfigurations variance out of [0.5, 2.0]" and would appreciate some guidance on resolving this issue.
I generated trial wavefunctions using QP and obtained determinant expansions of different scales by truncating CI coefficients:
Quintet state: When truncating the CI coefficients at 1e-5 (192,233 determinants) and 1e-4 (33,469 determinants), the following error occurs during VMC optimization (only optimizing the Jastrow factor, not the CI coefficients):

Safeguard failure: checkConfigurations variance out of [0.5, 2.0] * reference! Please report this bug.

However, truncating at 1e-3 (3,177 determinants) does not produce this error, and the VMC and subsequent DMC calculations complete successfully.
Triplet state: Similarly, truncating at 1e-8 and 1e-4 results in the same error, while truncating at 1e-3 (3,958 determinants) proceeds normally.

Questions
Is this error related to the excessive number of determinants?
What are the recommended strategies to resolve this issue and successfully run optimizations with larger determinant sets?

Thank you for your valuable time and assistance!