Concept 2 - Loose Foot Straps

[JaapvanE]

Check the routing of the straps in the buckle. I've never used an erg where the foot stretcher belt slipped once tightened, even old ergs.

That is how mine came out of the box. I can inmagine with a combiation of sweat, tears and grease they might start to slip, but a good cleaning might fix that.