Remote epitaxy exploits substrate interactions transmitted across atomically thin materials to replicate substrate crystal structure. Here we show that competition among graphene-, substrate-, and reconstruction-derived interactions can instead produce frustration. Using GdAuGe films on N-layer graphene/SiC(0001), we identify at intermediate N a self-limited interfacial state with broken long-range translational order, accompanied by non-monotonic crystallographic orientation selection in the epitaxial film above. The frustrated interface is accompanied by strongly enhanced magnetic irreversibility above 300 K, with an interface-dominated rather than volume-scaled response, linking epitaxial frustration to an emergent collective property. Annealing drives an initially epitaxial crystal into the frustrated state, distinguishing it from kinetically trapped disorder. First-principles calculations reveal a multi-periodic interfacial potential that provides a microscopic basis for frustration. Together, these results establish epitaxial frustration as a materials-design principle for stabilizing correlated interfacial states and emergent collective properties.