Only a DIY'er here, usually safe and competent enough to fix straight forward problems, but this one has me stumped. I have two outside lighting circuits running through Lutron RA2 dimmers. Both go back to a Hager MTN106 RCD. All been working fine for over a year, but now the breaker keeps tripping. All LED lamps and well within 150w capacity of each dimmer controller. Common feed from the RCD split to the two circuits, and I can leave either circuit connected independently without problems. As soon as I connect both circuits, the RCD trips. Changed the Wago connector blocks hooking it all together in the junction box and tried a differnet RCD but the same problem. All installed by a qualified electrician, but assumed it would be an easy fix without calling him back. Any ideas?