Abstract: High density stellarator operation is a promising scenario for a future fusion reactor. However, operating scenarios may be constrained by pressure-driven instabilities. The core density collapse (CDC) is a fast, pressure-driven loss of confinement that affects super-dense core (SDC) operation on the Large Helical Device. Previous work indicates that the CDC is triggered by a high-n ballooning mode in the bad-curvature region. The ballooning mode nonlinearly couples to a low-n mode in the core, and energy is inverse-cascaded into core mode, perturbing flux surfaces and causing the ejection of up to 50% of core density. To study high-resolution profile dynamics during the CDC, the instability was deliberately provoked with excessive pellet fueling of the core. Over 150 CDC events were produced. The first high-resolution temperature and density profile measurements of a CDC were made with a 20 kHz Thomson scattering diagnostic. A hot, narrow feature in the $T_e$ profile was observed during the CDC for the first time. The feature occupies about a quarter of the plasma diameter and lasts upwards of 150 $\mu$s before it collapses. This feature is hypothesized to be caused by either the transfer of kinetic energy from the ballooning mode to a core mode via nonlinear coupling or by an increase in localized NBI deposition caused by rapid changes to the density profile. The electron temperature feature is observed to collapse about 100 microseconds before core density, suggesting that multiple transport mechanisms may be at work. Density loss gradually propagates inward, from the transport barrier towards the magnetic axis. High resolution measurements of profile dynamics broadly agree with simulation predictions, although questions about the electron temperature feature and transport mechanisms remain. CDCs demonstrate that the ballooning mode places a hard limit on the accessible pressure gradient in stellarators.