Proper Ethernet Switch Settings

I have a SONOS system that has been working since 2017 with no major issues to report. I have three TP-LINK Manager Switches configured as follows:

TP-LINK T2600-52TS - Primary Switch
STP Turned ON
SONOS STP Path Cost = 10
Switch STP Path Cost =4
CIST Priority = 4096
Hello Time = 2 Seconds
Max Age = 20 Seconds
Forward Delay = 15 Seconds
TX Hold Count = 5 pps
MAX Hops = 20

Wired SONOS Components = 7
Wired Ethernet Switches = 3

Xfinity XB7 Modem is connected to this switch.


TP-LINK T2500-10TS - Remote Switch #1
STP Turned ON
SONOS STP Path Cost = 10
Switch STP Path Cost =4
CIST Priority = 8192
Hello Time = 2 Seconds
Max Age = 20 Seconds
Forward Delay = 15 Seconds
TX Hold Count = 5 pps
MAX Hops = 20

Wired SONOS Components = 2
Wired Ethernet Switches = 1 (Back to Primary Switch)


TP-LINK TL-SG3210 - Remote Switch #2
STP Turned ON
SONOS STP Path Cost = 10
Switch STP Path Cost =4
CIST Priority = 8192
Hello Time = 2 Seconds
Max Age = 20 Seconds
Forward Delay = 15 Seconds
TX Hold Count = 5 pps
MAX Hops = 20

Wired SONOS Components = 0
Wired Ethernet Switches = 1 (Back to Primary Switch)
NAS3 Connection -- Backup SONOS and Zappiti Media Storage - SYNOLOGY DS1821+


TP-LINK TL-T2600G-28TS - Remote Switch #3
STP Turned ON
SONOS STP Path Cost = 10
Switch STP Path Cost =4
CIST Priority = 8192
Hello Time = 2 Seconds
Max Age = 20 Seconds
Forward Delay = 15 Seconds
TX Hold Count = 5 pps
MAX Hops = 20

Wired SONOS Components = 0
Wired Ethernet Switches = 1 (Back to Primary Switch)
NAS1 Connection -- Primary SONOS and Zappiti Media Storage - SYNOLOGY DS1821+
NAS2 Connection -- General Storage - SYNOLOGY DS1511+



This configuration has worked well since 2017 when we moved into the new house. We had a bunch of power outages / blips over the last few weeks and since then the SONOS system is dropping and skipping while playing music from a SYNOLOGY NAS connected to Remote Switch #3. All wired SONOS and TP-LINK Interconnect ports have STP turned on with a STP Path Cost =4.

Questions:

1. Are my STP Path Cost correct for the connected devices?
2. Is the CIST Priority set correctly?
3. Do I need to set the STP Root Guard protection on the primary switch?