Not an expert but you logs make it look like there’s Network problems and/or Database read issues as this appears a lot in your logs.
Jul 08, 2021 04:40:00.217 [0x14da24fdcb38] WARN - SLOW QUERY: It took 330.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.224 [0x14da24d10b38] WARN - SLOW QUERY: It took 270.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.226 [0x14da24834b38] WARN - SLOW QUERY: It took 280.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.233 [0x14da24c0eb38] WARN - SLOW QUERY: It took 260.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.234 [0x14da245e3b38] WARN - SLOW QUERY: It took 210.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.247 [0x14da24cedb38] WARN - SLOW QUERY: It took 220.000000 ms to retrieve 76 items.
Jul 08, 2021 04:40:00.261 [0x14da23297b38] WARN - SLOW QUERY: It took 220.000000 ms to retrieve 53 items.
Jul 08, 2021 04:40:00.289 [0x14da24e15b38] WARN - SLOW QUERY: It took 220.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.315 [0x14da24dd0b38] WARN - SLOW QUERY: It took 260.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.316 [0x14da249d0b38] WARN - SLOW QUERY: It took 240.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.323 [0x14da24cedb38] WARN - SLOW QUERY: It took 210.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.324 [0x14da24e50b38] WARN - SLOW QUERY: It took 230.000000 ms to retrieve 48 items.
Jul 08, 2021 04:40:00.327 [0x14da24975b38] WARN - SLOW QUERY: It took 250.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.387 [0x14da24d10b38] WARN - SLOW QUERY: It took 340.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.423 [0x14da23297b38] WARN - SLOW QUERY: It took 220.000000 ms to retrieve 53 items.
Jul 08, 2021 04:40:00.441 [0x14da24dadb38] WARN - SLOW QUERY: It took 220.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.441 [0x14da24975b38] WARN - SLOW QUERY: It took 220.000000 ms to retrieve 42 items.
Jul 08, 2021 04:40:00.455 [0x14da24c0eb38] WARN - SLOW QUERY: It took 240.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.476 [0x14da26c5fb38] WARN - SLOW QUERY: It took 280.000000 ms to retrieve 59 items.
Jul 08, 2021 04:40:00.501 [0x14da25072b38] WARN - SLOW QUERY: It took 270.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.503 [0x14da24e50b38] WARN - SLOW QUERY: It took 230.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.504 [0x14da24fb9b38] WARN - SLOW QUERY: It took 300.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.517 [0x14da24dd0b38] WARN - SLOW QUERY: It took 250.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.533 [0x14da24cedb38] WARN - SLOW QUERY: It took 250.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.534 [0x14da24834b38] WARN - SLOW QUERY: It took 210.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.537 [0x14da249d0b38] WARN - SLOW QUERY: It took 250.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.540 [0x14da24c0eb38] WARN - SLOW QUERY: It took 360.000000 ms to retrieve 94 items.
Jul 08, 2021 04:40:00.548 [0x14da23297b38] WARN - SLOW QUERY: It took 260.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.560 [0x14da24606b38] WARN - SLOW QUERY: It took 250.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.567 [0x14da26c5fb38] WARN - SLOW QUERY: It took 240.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.605 [0x14da24fb9b38] WARN - SLOW QUERY: It took 230.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.610 [0x14da24606b38] WARN - SLOW QUERY: It took 210.000000 ms to retrieve 69 items.
Jul 08, 2021 04:40:00.612 [0x14da24dadb38] WARN - SLOW QUERY: It took 280.000000 ms to retrieve 63 items.
Jul 08, 2021 04:40:00.633 [0x14da245e3b38] WARN - SLOW QUERY: It took 390.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:00.645 [0x14da24930b38] WARN - SLOW QUERY: It took 290.000000 ms to retrieve 1 items.
Jul 08, 2021 04:40:01.737 [0x14da26a75b38] ERROR - Network Service: Error in advertiser handle read: 125 (Operation canceled) socket=81
Jul 08, 2021 04:40:01.783 [0x14da294ddb38] WARN - JobManager: Could not find job for handle 304
Jul 08, 2021 04:40:01.838 [0x14da26a75b38] INFO - Network Service: Abandoning advertise socket, it was closed.
Jul 08, 2021 04:40:01.841 [0x14da2c342b40] INFO - Killing process: Plex EAE Service (pid: 1162)
Jul 08, 2021 04:40:01.841 [0x14da2c342b40] INFO - Killing process: Plex Media Scanner (pid: 10597)
Jul 08, 2021 04:40:01.849 [0x14da237f9b38] ERROR - ChapterThumbsManager: job for item 71505 failed (-9)
Also I noticed your Plex opened up 36 Connections right before the errors kicked in
Jul 07, 2021 22:58:31.456 [0x14da22adbb38] DEBUG - Request: [192.168.2.24:64806 (Subnet)] PUT /:/prefs?LogVerbose=0&logDebug=0 (36 live) TLS GZIP