It’s still scanning media. These particular files generate a huge amount of output
Dec 28, 2020 11:03:21.852 [0x7f0b0111f700] DEBUG - Mp4AtomParser: Found 0x7000000 atom of size 29 at offset 5350395
Dec 28, 2020 11:03:21.852 [0x7f0b0111f700] DEBUG - Mp4AtomParser: Found data atom of size 21 at offset 5350403
Dec 28, 2020 11:03:21.852 [0x7f0b0111f700] DEBUG - Mp4AtomParser: Found 0x8000000 atom of size 33 at offset 5350424
Dec 28, 2020 11:03:21.852 [0x7f0b0111f700] DEBUG - Mp4AtomParser: Found data atom of size 25 at offset 5350432
Dec 28, 2020 11:03:21.852 [0x7f0b0111f700] DEBUG - Mp4AtomParser: Found 0x9000000 atom of size 28 at offset 5350457
Dec 28, 2020 11:03:21.852 [0x7f0b0111f700] DEBUG - Mp4AtomParser: Found data atom of size 20 at offset 5350465
Dec 28, 2020 11:03:21.852 [0x7f0b0111f700] DEBUG - Mp4AtomParser: Found 0xa000000 atom of size 48 at offset 5350485
Dec 28, 2020 11:03:21.852 [0x7f0b0111f700] DEBUG - Mp4AtomParser: Found data atom of size 40 at offset 5350493
Dec 28, 2020 11:03:21.852 [0x7f0b0111f700] DEBUG - [MI] Closing input file: "/volume3/Shire Photo/matt 11/IMG_2859.MOV"
Dec 28, 2020 11:03:21.853 [0x7f0b0111f700] DEBUG - Updating media item 16285, size=5350533, metadata_item_id=16370
Dec 28, 2020 11:03:21.853 [0x7f0b0111f700] DEBUG - Updating part with ID=16285 [/volume3/Shire Photo/matt 11/IMG_2859.MOV]
Dec 28, 2020 11:03:21.856 [0x7f0b0111f700] DEBUG - Updating metadata item (save) (IMG_2859) with ID 16370
Dec 28, 2020 11:03:21.857 [0x7f0b21c1e700] DEBUG - Updating metadata item (save) (IMG_2859) with ID 16370
Dec 28, 2020 11:03:21.860 [0x7f0b0111f700] DEBUG - Analyzing media parts for item 31443 (simple.m.ts.islb.se40.vmb): 31047
Dec 28, 2020 11:03:21.860 [0x7f0b0111f700] DEBUG - [ID 31047] Media part analysis: /volume3/Shire Photo/Storage/Work/Tech Track B/05B/simple.m.ts.islb.se40.vmb.avi
Dec 28, 2020 11:03:21.860 [0x7f0b0111f700] DEBUG - [MI] Opening input file: "/volume3/Shire Photo/Storage/Work/Tech Track B/05B/simple.m.ts.islb.se40.vmb.avi"
Dec 28, 2020 11:03:21.860 [0x7f0b0111f700] DEBUG - [FFMPEG] - Opening '/volume3/Shire Photo/Storage/Work/Tech Track B/05B/simple.m.ts.islb.se40.vmb.avi' for reading
Dec 28, 2020 11:03:21.860 [0x7f0b0111f700] DEBUG - [FFMPEG] - Setting default whitelist 'file,crypto'
Dec 28, 2020 11:03:21.860 [0x7f0b0111f700] DEBUG - [FFMPEG] - Format avi probed with size=2048 and score=100
Dec 28, 2020 11:03:21.860 [0x7f0b0111f700] DEBUG - [FFMPEG] - use odml:1
Dec 28, 2020 11:03:21.861 [0x7f0b0111f700] DEBUG - [FFMPEG] - Before avformat_find_stream_info() pos: 4096 bytes read:109204 seeks:4 nb_streams:1
Dec 28, 2020 11:03:21.861 [0x7f0b0111f700] DEBUG - [FFMPEG] - All info found
Dec 28, 2020 11:03:21.861 [0x7f0b0111f700] DEBUG - [FFMPEG] - After avformat_find_stream_info() pos: 27680 bytes read:109204 seeks:4 frames:1
Dec 28, 2020 11:03:21.861 [0x7f0b0111f700] DEBUG - [MI] * d28a404fded3ec39c65b7ef0dd9019816817635e [avi msrle/] Duration: 32900ms, 1270x924 (1.374459) 10.000fps, bitrate=1899kbps, audio channels=0, optimizedForStreaming=0 ("/volume3/Shire Photo/Storage/Work/Tech Track B/05B/simple.m.ts.islb.se40.vmb.avi")
Dec 28, 2020 11:03:21.861 [0x7f0b0111f700] DEBUG - [MI] Chapters had generic titles, clearing.
Dec 28, 2020 11:03:21.861 [0x7f0b0111f700] DEBUG - Updating metadata item (save) (simple.m.ts.islb.se40.vmb) with ID 31443
Dec 28, 2020 11:03:21.862 [0x7f0b0111f700] DEBUG - [MI] Closing input file: "/volume3/Shire Photo/Storage/Work/Tech Track B/05B/simple.m.ts.islb.se40.vmb.avi"
Dec 28, 2020 11:03:21.863 [0x7f0b0111f700] DEBUG - Committing media stream changes for part 31047
Dec 28, 2020 11:03:21.863 [0x7f0b0111f700] DEBUG - Updating media item 31047, size=7810048, metadata_item_id=31443
Dec 28, 2020 11:03:21.863 [0x7f0b0111f700] DEBUG - Updating part with ID=31047 [/volume3/Shire Photo/Storage/Work/Tech Track B/05B/simple.m.ts.islb.se40.vmb.avi]
Dec 28, 2020 11:03:21.866 [0x7f0b0111f700] DEBUG - Updating metadata item (save) (simple.m.ts.islb.se40.vmb) with ID 31443
Dec 28, 2020 11:03:21.868 [0x7f0b21c1e700] DEBUG - Updating metadata item (save) (simple.m.ts.islb.se40.vmb) with ID 31443
Dec 28, 2020 11:03:21.871 [0x7f0b0111f700] DEBUG - MetadataItemClusterRequestHandler: 16 unclustered items have been processed
Dec 28, 2020 11:28:17.978 [0x7f0b0111f700] DEBUG - Sync: uploadStatus
Dec 28, 2020 11:28:30.592 [0x7f0b02e6b700] DEBUG - Putting plug-in com.plexapp.agents.imdb to sleep.
Dec 28, 2020 11:28:30.592 [0x7f0b02e6b700] DEBUG - Stopping [com.plexapp.agents.imdb].
Dec 28, 2020 11:28:30.592 [0x7f0b02e6b700] DEBUG - [com.plexapp.agents.imdb] Killing.
Dec 28, 2020 11:28:30.594 [0x7f0b28acc700] WARN - JobManager: Could not find job for handle 7733
Dec 28, 2020 11:28:40.593 [0x7f0b02e6b700] DEBUG - Stopping file watcher for com.plexapp.agents.imdb
Dec 28, 2020 11:58:17.978 [0x7f0b01cd7700] DEBUG - Sync: uploadStatus
Dec 28, 2020 12:28:17.979 [0x7f0b01cd7700] DEBUG - Sync: uploadStatus
Dec 28, 2020 12:58:17.979 [0x7f0b0111f700] DEBUG - Sync: uploadStatus
Dec 28, 2020 13:28:17.979 [0x7f0b01cd7700] DEBUG - Sync: uploadStatus
Dec 28, 2020 13:58:17.980 [0x7f0b01cd7700] DEBUG - Sync: uploadStatus```
Pull open the Synology Resource Monitor.
Watch the CPU loading.
Just because the Plex/Web UI looks idle doesn't mean the CPU isn't doing scanning in the background (above)