King Dubby Delay - Sounds extremely distorted

[GrooveChampion]

I recently finished building this, it works but the repeats are extremely distorted and it oscilates if the repeats knob is turned even slightly.

I used a 3mm bright LED instead of the 5mm difused and sadly my PT2399 chips are DTC not PTC, I will try to post pics tomorrow, any ideas as to what this could be?

[GrooveChampion]