r/LGTVOwners

Denon X1800H + LG C5 + Shield/PS5 – CEC power & input switching broken after working fine

Looking for help diagnosing HDMI-CEC / power and input switching issues in my setup.

Gear:

TV: LG C5 OLED TV (87")

AVR: Denon AVR-X1800H

Sources on denon: PlayStation 5 + NVIDIA Shield TV

Everything was working perfectly before—CEC power on/off and input switching were reliable. Then suddenly it stopped behaving properly.

Current issues:

Power on/off (CEC) is inconsistent.

Turning on a source (PS5 or Shield) doesn’t always power on the full chain.

Sometimes TV or AVR stays off, or turns on without syncing correctly

Input/source switching is unreliable

AVR sometimes switches to the correct input when a device turns on

Other times it either doesn’t switch or switches incorrectly.

Behavior feels random/inconsistent

System “confusion”.

Devices don’t seem to agree on active source

Occasional mismatches between what’s on and what input is selected.

When I turn on the shield the tv doesn't always turn on.

What I’ve tried:

Swapping HDMI cables, using 8k certified between all devices now.

Power cycling all devices.

Checking HDMI-CEC settings (Simplink on LG, HDMI Control on Denon).

Tried many different settings in every device.

Is this typical HDMI-CEC instability, or something specific to Denon + LG setups?

Any better “known stable” config (e.g., only one device controlling power)?

Would a full reset of the Denon AVR-X1800H help, or better to isolate first?

Could firmware or a stuck HDMI handshake state cause this sudden change?

Trying to decide whether to keep fighting CEC or just move to a universal remote setup.

Getting crazy with this setup and I believe the denon is the problematic one (I have a similar setup with a Sony receiver and it works perfectly)