Christmas lights or yard lights with switching DC power supplies are often the RFI source and a clamp on ferrite bead on the AC AND the DC side feeding the lights is needed to help suppress the switching power supply RFI noise. Suitable snap on beads are FSB31-1/2 for the 1-250 MHz range.
We have also had reported wireless HDTV boxes, and FOSCAM and AMCREST security camera systems causing RFI to garage door remote openers. Use our Garage Door Opener RFI kit to suppress the interference to the opener (VICTIM) – you need one kit for each opener. Maximize the distance from the camera to the openers may also help. Additionally shield cable to the garage door sensors may be needed depending on severity of the camera RFI.
Obvious Tech Note: make sure your remote batteries have enough energy to activate the GDO or the signal they transmit may not be large enough to over ride the RFI signal, but a fresh battery may be able to overcome the weak RFI source and allow the GDO to operate correctly.