In most cases, this type of problem is caused by either the plug not being pushed fully into place, or slight variations in 3.5mm jack plug designs. Some plugs have a slightly wider or more “bulbous” housing near the tip, which can prevent them from seating fully inside certain couplers, even though the connector itself is correctly sized. All of our couplers are manufactured to standard 3.5mm specifications, but there can be small tolerances between different brands of plugs and connectors which occasionally affect fit.