This is similar (in symptoms) to the problem of running out of tcp ports - however, the logs do not show excessive number of requests that could lead to using up the 16K dynamic tcp ports pool in windows
Do you run proxy software / vpn that may be interfering with the requests Plex is making for loopback (127.0.0.1) between Plex Media Scanner and Plex Transcoder and Plex Media Server processes ?
I can see the transcoder failing to make a loopback request to Plex Media Server process - eg
Feb 01, 2021 02:49:20.101 [18576] ERROR - [Transcoder] [tcp @ 007fee40] Connection to tcp://127.0.0.1:32400 failed: Error number -138 occurred
Feb 01, 2021 02:49:20.175 [19112] DEBUG - Jobs: 'C:\Program Files (x86)\Plex\Plex Media Server\Plex Transcoder.exe' exit code for process 14124 is 1 (failure)
and I can also see the scanner failing immediately when trying to make a request to the server process
Feb 01, 2021 00:25:35.823 [20300] ERROR - Error issuing curl_easy_perform(handle): 7
Feb 01, 2021 00:25:35.823 [20300] WARN - HTTP error requesting GET http://127.0.0.1:32400/:/metadata/notify/cullTimeline?librarySectionID=3&sinceTime=1612166735 (7, Couldn't connect to server) (Failed to connect to 127.0.0.1 port 32400: Address not available)
Feb 01, 2021 00:25:35.823 [12892] ERROR - Error issuing curl_easy_perform(handle): 7
Feb 01, 2021 00:25:35.823 [12892] WARN - HTTP error requesting PUT http://127.0.0.1:32400/activities/82b48906-7c0e-481f-9493-0ff83899f100?percentComplete=0 (7, Couldn't connect to server) (Failed to connect to 127.0.0.1 port 32400: Address not available)
As this is happening almost immediately rather than after thousands of requests, it suggests that there must be some external factor eg a vpn or proxy or perhaps some other program using up all the tcp ports in windows
You can eliminate the tcp port exhaustion issue by checking the Windows Event Log (Event Viewer → Windows Logs → System and filter for event ID 4227)
