My notes are currently in Dropbox, and also synced to my phone.
I wanted to migrate to Joplin Cloud and I've signed up, and entered the details in the phone app.
Clicked "Synchronise" and waited for it to complete. Clicked it again a few more times for good measure.
I can see a bunch of notes at joplincloud.com, that's good.
I can sync the notes to my laptop from joplincloud.com using the command line client. that's good.
There are missing notes from the last month. that's bad.
Then I synced from Dropbox. It created 644 local items, which doesn't seem like enough, because although the most recent notes were there, it only created 4 notebooks and 3 tags, when there are supposed to be 17 notebooks and dozens of tags (which I can see on the Android app on my old device).
Other checks I performed:
I changed the (correctly synced) Android app sync target to local filesystem, to find out how many items a full sync is supposed to have: it deleted 87 items, created 3271 remote items, and fetched 3266 items. That seems correct.
I checked the status of the Node command line client (which had been synced from Joplin Cloud), it seemed to be the correct number of items.
I did an export from the Node client: It created a tar file containing 3209 files (2995 markdown and 215 resources). That seems the correct number.
I used the Dropbox client (not Joplin) to fetch the App/Joplin directory and count the files in it: 644 markdown files and 7 files in .resource dir. That seems way too few.
After reading other questions and answers, I tried again with a sync target that I've never used before: OneDrive.
I synced Android Joplin client on my old device with a clean OneDrive account. Then I synced the Android Joplin on my new device with the OneDrive account.
Result:
About 1516 notes were synced, which seems like all of them
Zero notebooks were synced
Zero tags were synced
Is this a known issue?
My notes are not usable in the way I want, if they have no tags and are not in any notebooks.
I don't understand how I can continue to use Joplin when I encounter so many critical bugs.
I want to report that I have resolved the issues, by creating a new dropbox account which is dedicated to my joplin notes, and syncing that with the joplin app on my old device. I then deleted the ~/.config/joplin* data directories (which were not easy to find), and re-synced the node and desktop clients from the new dropbox account.
I'm disappointed that the root issues still exist, and the above solutions may be out of reach for some non-technical users. I would like to explore the options for adding functionality to "reset" the sync in case something odd happens like it did to me. Paramount is keep the users data safe (and reassure them of this), because fear of losing my notes data was the major blocker when I was troubleshooting these issues.
The desktop client covers a few things you mention here:
The data directory can be directly accessed from Joplin by Help > Open profile directory
There are two options within Config > Synchronisation > Show advanced settings called Re-upload local data to sync target and Delete local data and re-download from sync target
These generally cover most aspects of resetting the data on the sync targets and or client, I suspect your issue was somewhat of an edge case or at least I personally haven't seen this reported particularly often (although I'm happy to be corrected).
The simple backup plugin is also a recommended plugin for keeping desktop data safe - although it does require the desktop app but writing a chron job or something to do the same task with the terminal client shouldn't be difficult.