OP. I'm sure you have already checked this but I just want to verify your surround speakers are connected to the correct posts since you mentioned the sound alternating when you pressed the Speaker A/B button.
You should have a set of 8 clip-type receptacles ( 2 rows of 4 clips ) for your surround speakers. The TOP 4 clips are for the Right +,- and Left -,+ if you want to run TWO sets of front speakers. The bottom 4 clips are for speakers in surround mode. They are clearly labeled but if you are hooking them up with the receiver in a confined space, it would be easy to blindly choose the wrong clips.
If the speakers are wired correctly then run the HDMI from PS3 to TV and the TosLink from PS3 to receiver's Optical Input. Use one of the three you have depending on whatever source you want to come from when everything is turned on. If your Samsung TV has an Optical OUT, then you can run the TosLink from TV to Receiver using the Monitor Optical Input. You'll have to decide which is best for you based on the other components, like a Cable or Satellite Receiver, in your setup. There is probably a setting somewhere in the PS3 for changing the audio out from HDMI to Optical Digital depending on how you have to run the TosLink ( to Receiver or from TV ). It has been 5 years since I messed with a PS3. Also look for anything in your " Speaker Setup " menu that allows you to assign the amp sections to specific binding posts if the speakers are wired properly.
Denon AVR X7200WA, Emotiva XPR-5, Emotiva XPA-7, Sony XBR 75" 850C, Oppo BDP-103D, Roku 4.
DefTech BP7000SC (L/R), CLR3000 (C), SM55 (FH), UIW BPZ/A (SB), UIW 75 (TM).
JBL L7 (Sur), EoSone RSR 350 (RH).
PC 2.1 setup. Emotiva Stealth 6, SVS SB2000 sub, Emotiva DC-1 DAC.