Super simple patch:
Kick drum -
Gate -> ADSR (A-140-2) -> CVF A-105-2 -> Out
Ducking -
Kick drum -> A-119 -> Envelope Out -> A-138j (inverted) -> VCA processing bass synth.
The A-119 basically can’t distinguish a ‘clean enough’ kick sound to generate a smooth envelope. No issues with samples, use this setup all the time.