I finally found that thread after days or trying to understand why my setup became unusable after years of it working fine and switching to a new TV.
Both TVs are Philips, both with ambilight. Both will work with the same remote control.
The new one is larger (42", previous was 36") and has ambilight on 3 sides (top too).
My living room is painted white, so that doesn't help with reflections.
Away from the TV Flirc will work perfectly, I tested it as a keyboard on several machines (Linux and windows).
Next to the TV it works randomly. More often not at all.
I noticed I could sometimes get the Flirc to recognize my key presses if I wrap my hand around it, but even that is tricky.
So that confirms @chafry MacGyver's fix.
After lengthy tests I've been able to find a 10sec sequence in a movie that will prevent any key press to be registered when played. It's mainly a bright white logo.
Since both TV have ambilight and one works fine, I think @jason is right to suspect the new TV's backlight to be the culprit. @jason
Is there any plan to see an improvement to the firmware in a future update? The fact that my TV is able to read its remote seamlessly shows that interferences from ambilight or the TV backlight are not necessarily fatal to reading IR signals.
In the past it was possible to set a noise filter via the FLIRC GUI. This seems to have disappeared. Maybe that could have helped?
I really like my Flirc and it's been the perfect companion to my rasPlex for many years. I'd be very sad if I couldn't get it to run anymore.
If I can do anything to help with solving that issue I'd be glad to do so
First image: the sequence that paralyses Flirc
Second image: my setup :)
Third image: small TV worked, big TV doesn't