~~~~~~~~~~~~~~~
They seemed to have had a lot of trouble with the wireless mics on SP. There were a lot of instances of static, buzzing, belt packs not being turned on, etc., so I can see why they were avoided on P+.
That doesn't surprise me, particularly with all the neon on SP the set. It's why Barker never used a wireless. Wireless mics and neon don't agree. Having contestants crane their necks to see the game board was a another problem.
~~~~~~~~~~~~~~~
In the early episodes of SP, during the main game, they used to flash the neon border when one side won. You could hear plenty of wireless mic buzz during gameplay even without the flashing. Making goodbyes with extra "pulse" buzzing may have driven the change to keep the neon continuously lit instead. Just a guess, though...
Flashing neon interference didn't seem as noticeable during an end game win with crowd noise, music, etc.