What is the Reform UK funding scandal about?

Nigel Farage told allies he's been "taking stock" of his political future after Reform UK's Birmingham conference was overshadowed by a fresh funding row that forced out two senior aides, head of policy James Orr and long-serving confidant Dan Jukes, following a Channel 4 report [2]. Farage tried to move past the controversy by unveiling a platform of major tax cuts alongside significant spending cuts to bolster the party's economic credibility [1]. I don't have further detail here on exactly what the underlying funding allegations involve.