Audio Cutout - but only when sourcing from playbase or playbar

I have a playbar on one tv and a playbase on another tv, also several other play:1 play:3 and connect:Amp.
When I use my phone or laptop as a source and switch to 'party mode', everything is perfect - always.
When I watch either TV with only it's playbase or playbar - it works flawlessly.
If, however, I attempt to group any other speakers to either the playbase or playbar sourced by TV sound - the audio cuts out every few seconds. This just started fairly recently - I recall watching some football this way (party mode) with no issues the entire evening - but by the time playoffs rolled around - it's not usable in that way. I'm unable to think of any significant changes that have been made since I recall this working - maybe the playbase is that new - it arrived on christmas day. :)

Another interesting thing to note is that the source playbase or playbar (depending on which tv I want to broadcast) never cuts out - only the satellite grouped speakers cut out - and they all cut out together.

This occurs with 'smart app' sourced audio as well as DTV sourced audio - I'm quite confident it's not a tv/receiver audio output issue in that the two setups are completely different but are behaving identically - also - the 'main' speaker never cuts out.

I tried switching between BOOST and home wifi - no change.
Only a single play:1 is not hardwired to the Gigabit Cat6e LAN.
I tried disabling the wificontrol - no change.
External interference is unlikely - I don't have many neighbors nearby.

I ran the diagnostics: 8505842
Currently playing Netflix Smart TV App in Master Bedroom - grouped in party mode and cutting out everywhere but MasterBedroom Playbar.

Associated ZP: 192.168.5.235
---------------------------------
PLAY:3: Bathroom
Serial Number: B8-E9-37-D0-90-8A:1
Version: 8.3 (build 40549090)
Hardware Version: 1.8.1.3-1
IP Address: 192.168.5.172
WM: 0
OTP:
---------------------------------
PLAY:1: Kitchen (L)
Serial Number: 5C-AA-FD-4D-FE-A2:F
Version: 8.3 (build 40549090)
Hardware Version: 1.8.3.7-1
IP Address: 192.168.5.235
WM: 0
OTP:
---------------------------------
PLAY:1: Kitchen (R)
Serial Number: 5C-AA-FD-4E-01-F2:D
Version: 8.3 (build 40549090)
Hardware Version: 1.8.3.7-1
IP Address: 192.168.5.243
WM: 0
OTP:
---------------------------------
PLAYBASE: Living Room
Serial Number: 5C-AA-FD-32-F1-5D:8
Version: 8.3 (build 40549090)
Hardware Version: 1.14.1.11-1
IP Address: 192.168.5.196
Audio In:
WM: 0
---------------------------------
PLAYBAR: Master Bedroom
Serial Number: 5C-AA-FD-17-9A-19:D
Version: 8.3 (build 40549090)
Hardware Version: 1.9.1.10-1
IP Address: 192.168.5.241
Audio In: Dolby Digital 2.0
WM: 0
OTP:
---------------------------------
PLAY:3: Office
Serial Number: B8-E9-37-DC-5C-42:8
Version: 8.3 (build 40549090)
Hardware Version: 1.8.1.3-1
IP Address: 192.168.5.208
WM: 0
OTP:
---------------------------------
CONNECT:AMP: Patio
Serial Number: 5C-AA-FD-EA-20-AE:D
Version: 8.3 (build 40549090)
Hardware Version: 1.17.3.1-1
IP Address: 192.168.5.60
WM: 0
OTP: 1.1.1(1-17-3-2.1)