This paper investigates the convergence issues in the finite element solution of the bi-curl (double curl) equation, with a particular focus on the critical role of the discrete representation of the right-hand side (source term). Numerical experiments demonstrate that incompatibility between the discrete source term and the finite element space may lead to convergence failure or numerical instability. To address this, a source-field-based correction strategy is proposed. By modifying the vector potential in the current-carrying region, the current density is expressed as the curl of an auxiliary field, which is then projected onto the Whitney edge element space. This correction ensures compatibility between the source term and the finite element space, thereby improving the stability and convergence of the numerical solution.