Bond disorder in frustrated pyrochlore antiferromagnets can give rise to fundamentally different quantum ground states depending on the nature of the local magnetic moments. Here, we show that the bond-disordered $J_{\mathrm{eff}}=\frac{1}{2}$ pyrochlore antiferromagnet ${\mathrm{NaCdCo}}_2{\mathrm{F}}_7$ realizes an unconventional spin-glass-like state with continued dynamics, in stark contrast to its isostructural $S=\frac{1}{2} {\mathrm{NaCdCu}}_2{\mathrm{F}}_7$ counterpart. High-field magnetization and Co $L_{2,3}$-edge x-ray absorption spectroscopy/x-ray magnetic circular dichroism establish spin-orbit-entangled $J_{\mathrm{eff}}=\frac{1}{2} {\mathrm{Co}}^{2+}$ moments with a substantial unquenched orbital contribution, consistent with local $XY$ anisotropy seen in the isostructural $\mathrm{Na}{A}^{\prime \prime }{\mathrm{Co}}_2{\mathrm{F}}_7$ ($A^{\prime \prime }=\text{Ca}$, Sr) analogs. muon spin relaxation and ${}^{23}\mathrm{Na}$ nuclear magnetic resonsonance (NMR) measurements reveal progressive slowing of spin fluctuations below $\sim 10\mathrm{K}$, culminating in a partially frozen state with persistent low-temperature dynamics that deviates from a canonical spin glass. Comparison with the isostructural bond-disordered pyrochlore ${\mathrm{NaCdCu}}_2{\mathrm{F}}_7$, which realizes a random-singlet state, reveals a fundamentally different response of spin-orbit-entangled ${\mathrm{Co}}^{2+}$ moments to bond disorder. These results identify spin-orbit coupling as a key ingredient governing the fate of bond-disordered frustrated pyrochlore magnets.

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• Frustrated magnetism
• High magnetic fields
• Spin dynamics
• Spin-orbit coupling
• Disordered systems
• Pyrochlores
• Spin glasses
• Muon spin relaxation & rotation
• Nuclear magnetic resonance
• X-ray magnetic circular dichroism