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Given the multifrequency nature of relativistic orbits, transient orbital resonances are expected to be ubiquitous during an extreme-mass-ratio inspiral (EMRI). At a resonance, the orbital dynamics is modified in a nontrivial way, imprinting an overall dephasing in the emitted gravitational waves and potentially impacting both the detection and parameter estimation of these sources. In this work, using a Fisher-matrix approach, we investigate the bias induced by transient orbital resonances in EMRI parameter estimation. We focus on the most dynamically significant low-order resonances, <inline-formula><mml:math><mml:mn>3</mml:mn><mml:mo>:</mml:mo><mml:mn>2</mml:mn></mml:math></inline-formula> and <inline-formula><mml:math><mml:mn>2</mml:mn><mml:mo>:</mml:mo><mml:mn>1</mml:mn></mml:math></inline-formula>, as well as on the high-order, subdominant resonances, <inline-formula><mml:math><mml:mn>3</mml:mn><mml:mo>:</mml:mo><mml:mn>1</mml:mn></mml:math></inline-formula> and <inline-formula><mml:math><mml:mn>4</mml:mn><mml:mo>:</mml:mo><mml:mn>3</mml:mn></mml:math></inline-formula>. We find that, for most of the orbits considered, neglecting the effect of a resonance crossing leads to significant losses in signal-to-noise ratio and induces bias in parameter recovery. Furthermore, both the sign and the amplitude of the resonance-induced modifications to the integrals of motion play a crucial role and must be modeled accurately. Our results provide further evidence that failing to model transient orbital resonances accurately can hinder EMRI detection and parameter estimation, thereby limiting their scientific potential.

We study the quasinormal spectrum of a massive test scalar field in the exact asymptotically flat regular black-hole geometry supported by a phantom Dirac─Born─Infeld scalar. Using high-order WKB approximation improved by Padé resummation, together with characteristic time-domain integration and Prony extraction, we compute the fundamental mode and the first two overtones for representative values of the regularity parameter and the field mass. We show that increasing the field mass raises the oscillation frequency and reduces the damping rate, while increasing the regularity scale generally makes the ringing softer and longer lived. The time-domain profiles are in very good agreement with the WKB─Padé results and confirm the robustness of the spectrum. For sufficiently large field mass, the damping tends to zero, indicating the onset of quasiresonant behavior, although in the time domain these modes are eventually masked by oscillatory late-time tails. Our results show that massive scalar ringing provides a sensitive probe of this DBI-supported regular geometry.