LFO not working for Hardcoded FX

[DanH]

Please see below. In my instrument module's FX rack I have a stock Hise gain and a Hardcoded FX. The LFO modulating the stock gain works perfectly but there's no response from the Hardcoded FX. I've enabled 'External Modulation' for the control in scriptnode before compiling the network. Perhaps there's something else I need to do?