I have the same HDMI flicker on my Westy W32W6 LCD. That's HDMI not my A2. I have an early A2 built in Japan currently running v 2.7.
You will see if you change resolution in the set-up as well. That's just a fun HDMI handshake. I bet your set is the culprit. BTW, it's more a flash than a flicker, I see a magenta, then a black, then a green screen in rapid succession for like 2 seconds before the handshake is locked. The player needs to verify HDCP and that the display can handle the resolution. HDMI is a buggy mess. However, we're stuck with it.