From your logs:
Jun 09, 2018 09:24:59.968 [0x7f7c77317700] WARN - NAT: UPnP, error mapping port 13642, error: Invalid Args, controlURL: http://192.168.1.1:5000/Public_UPNP_C3.
Jun 09, 2018 09:25:02.392 [0x7f7c70e6b700] ERROR - Failed to begin transaction (../Library/MetadataCollection.cpp:335) (tries=1): Cannot begin transaction. database is locked
Jun 09, 2018 09:39:54.028 [0x7f7c705a1700] WARN - SLOW QUERY: It took 300.000000 ms to retrieve 50 items.
Jun 09, 2018 09:40:08.067 [0x7f7c6fcd7700] WARN - SLOW QUERY: It took 420.000000 ms to retrieve 50 items.
Jun 09, 2018 09:42:26.065 [0x7f7c7088f700] WARN - SLOW QUERY: It took 420.000000 ms to retrieve 50 items.
Jun 09, 2018 09:42:35.057 [0x7f7c76a4d700] WARN - SLOW QUERY: It took 460.000000 ms to retrieve 50 items.
Jun 09, 2018 09:43:58.741 [0x7f7c76471700] INFO - [PlexRelay] Allocated port 4235 for remote forward to localhost:32401
Jun 09, 2018 10:42:24.984 [0x7f7c758b9700] ERROR - Throttle: timed out trying to read chunk 84
Jun 09, 2018 10:56:52.597 [0x7f7c79911700] ERROR - Couldn't get remote endpoint: remote_endpoint: Transport endpoint is not connected
Jun 09, 2018 10:56:52.597 [0x7f7c79911700] ERROR - Couldn't get remote endpoint port: remote_endpoint: Transport endpoint is not connected
Jun 09, 2018 10:56:52.636 [0x7f7c7088f700] WARN - Failed to set up two way stream, caught exception: write: Connection reset by peer
Jun 09, 2018 11:22:26.023 [0x7f7c702b3700] ERROR - [Transcoder] [mp4 @ 0x23eefc0] Application provided duration: -1 / timestamp: 54721333 is out of range for mov/mp4 format
Jun 09, 2018 11:29:44.676 [0x7f7c70b7d700] WARN - Transcode runner appears to have died.
Jun 09, 2018 20:25:05.325 [0x7f7c77605700] WARN - Unable to load episode file ["seasons/1/episodes/1.xml"]
Jun 11, 2018 00:48:05.328 [0x7f7c77be1700] INFO - Library section 1 (TV Shows) will be updated because of a change in /volume1/Videos/Television/Westworld/Season 2
Jun 11, 2018 00:13:17.116 [0x7f1ec3fd6800] ERROR - Exception analyzing media file '/volume1/Videos/Anime/Series/Escaflowne/The Vision of Escaflowne - 26 - Eternal Love.mp4' (Could not parse /volume1/Videos/Anime/Series/Escaflowne/The Vision of Escaflowne - 26 - Eternal Love.mp4 (error=-1094995529): Invalid data found when processing input)
You have many problems to deal with. Start by rebooting your modem/router and everything connected to it including any wireless devices.
Then make sure the port forward rule in your router uses TCP, port 32400, and it points to your NAS IP Address. Then go to Plex settings > server > remote access > show advanced and make sure you have ‘Manually specify public port’ enabled and leave it set to 32400 then click on apply. Don’t forget to click on Save Changes.
It is also a good idea to give the NAS a static IP Address, or if your router supports it, use DHCP Reservation.
Then you need to do the following several times:
- Optimise Database
- Empty Trash
- Clean Bundles
Wait for each step to complete before moving to the next step.
Next, I recommend that you organise your media according to Q5 on the Synology FAQ’s page, link in my signature. The default Video folder is intended for use by Video Station and it has been known to cause issues with Plex in the past.
And finally, but not least, you need to check ALL of your media files for errors and correct them by either replacing the file or by re-encoding the file. See Q17 & Q28 on the Synology FAQ’s page, link in my signature.