No attachments in mattermost after import of Slack Advanced Exporter file via CLI or mmetl

No, something else - both the --validate and the --apply start with these

{"level":"info","ts":1606398571.003683,"caller":"utils/i18n.go:83","msg":"Loaded system translations","for locale":"en","from locale":"/opt/mattermost/i18n/en.json"}
{"level":"info","ts":1606398571.0038996,"caller":"app/server_app_adapters.go:58","msg":"Server is initializing..."}
{"level":"info","ts":1606398571.0068812,"caller":"sqlstore/supplier.go:227","msg":"Pinging SQL","database":"master"}
{"level":"info","ts":1606398571.1148207,"caller":"mlog/log.go:167","msg":"Starting up plugins"}
{"level":"info","ts":1606398571.1149483,"caller":"app/plugin.go:202","msg":"Syncing plugins from the file store"}
{"level":"error","ts":1606398571.553881,"caller":"app/plugin.go:793","msg":"Failed to install prepackaged plugin","path":"/opt/mattermost/prepackaged_plugins/mattermost-plugin-nps-v1.0.4-linux-amd64.tar.gz","error":"Failed to install extracted prepackaged plugin /opt/mattermost/prepackaged_plugins/mattermost-plugin-nps-v1.0.4-linux-amd64.tar.gz: installExtractedPlugin: Unable to move plugin from temporary directory to final destination. Another plugin may be using the same directory name., destination already exists","errorVerbose":"installExtractedPlugin: Unable to move plugin from temporary directory to final destination. Another plugin may be using the same directory name., destination already exists\nFailed to install extracted prepackaged plugin /opt/mattermost/prepackaged_plugins/mattermost-plugin-nps-v1.0.4-linux-amd64.tar.gz\ngithub.com/mattermost/mattermost-server/v5/app.(*App).processPrepackagedPlugin\n\tgithub.com/mattermost/mattermost-server/v5/app/plugin.go:845\ngithub.com/mattermost/mattermost-server/v5/app.(*App).processPrepackagedPlugins.func2\n\tgithub.com/mattermost/mattermost-server/v5/app/plugin.go:791\nruntime.goexit\n\truntime/asm_amd64.s:1373"}
{"level":"info","ts":1606398571.5779762,"caller":"app/server.go:273","msg":"Current version is 5.25.0 (5.25.2/Fri Jul 31 12:28:34 UTC 2020/7c21fabef8a03c0e130da73cd8419f263c876e32/none)","current_version":"5.25.0","build_number":"5.25.2","build_date":"Fri Jul 31 12:28:34 UTC 2020","build_hash":"7c21fabef8a03c0e130da73cd8419f263c876e32","build_hash_enterprise":"none"}

This is followed by many of these:

{"level":"error","ts":1606398579.6887288,"caller":"app/import_functions.go:1361","msg":"Error attaching files to post.","post_id":"k6wr8detnpyj7euaxp48sbx47y","post_file_ids":["4f8oabacctro5cd9obmf1b143o"],"error":"SqlFileInfoStore.AttachToPost: Unable to attach the file info to the post., post_id=k6wr8detnpyj7euaxp48sbx47y, file_id=4f8oabacctro5cd9obmf1b143o"}