Thank you guys.
I'm migrating content from another tool.
The content of these documents is of the same type: tons of small tables with reference data (command-value-example)...no images or special text, no lists, no links...the table sizes vary are between 2-3 columns and 4-15 rows. Each table comes with a Heading as section title that would become page title in wiki, no table caption and no text (paragraph) longer than a few sentences (and that only in a very few places).
What I usually do is the following:
1. Open the FM file, and 'Save As' rtf.
2. Open the rtf file in Word and 'Save as' docx.
3. Remove all Headers & Footers.
4. Line by line reformat the whole docx and apply the MS Word's built-in default styles. All text will be formatted to Normal, all Headings formatted using the built-in heading styles...
5. Import the docx to wiki
Ususally I have no problem with the execution... cca 750 pages of the 905 pages long reference document I've been working on has been successfuly migrated this way, and today morning I continued with a few, 10-50 pages long document, again, with success regarding importing.
Then about noon (CET) it started to throw bugs at me...
- first the imports were succesful but the content disappeared (not visible in Reorder or Hidden, Orphan, etc - nowhere).
- Then I imported again, this time I got the message that 'a page with the same title already exists in this workspace, choose another title for this page' (not exactly this, but sg like this).
- Then all exports failed, whatever I tried...e.g. splitting the content to chapters, making the content less 'deep' so we have less Heading levels (I only allow 3 usually, this time I restricted this to 2 Heading levels), also tried to create a doc file with 'Save As' from the docx, or create new word files from scratch, etc.
Nothing worked (and we can't access the logs, so I only have the error message to show you - pls find attached).
A few of my trial-error couplings ended up with me creating a separate space for the Buggy imports, because in spite the error message, pages started to show up and they were WEIRD, I mean it didn't make sense: the import created one page per CELL. I have 69 tables in that part of the document, so since mass deletion is not really possible for me, I added these to the same parent and then move the parent and its hundreds of children to the buggy imports space.
I'm not sure if any of these unsuccessful imports will show up in the page tree tomorrow, but I really hope they won't because it's simply impossible to clean the whole thing up again (the Table of Contents for this 905 pages long documents is 27 pages long. That's 400 wiki pages approximately).
This evening, after working hours I tried again. First, I created brand new docx files from scratch, empty, and pasted the content. Did the usual reformatting to make sure no 'external' or hidden formatting contaminate the file...I got 20+ files this way (each between 10-20 pages long).
This worked, they were imported with a success message, and look ok to me (the usual raw format we get after importing tables from word).
I wonder if the problem was that there was insufficient cloud server capacity for processing all imports...

Hi everyone,
Thank you for previously raising this bug and bringing it to our attention.
Within our company roadmap and work capacity, we try to address or review each bug request but admit that not each one will be resolved. To continue the culture of being honest and open, we are closing this bug to focus on our upcoming roadmap for all Confluence users.
As we continue to roll out features we do look at requests made by our users and if you feel like this bug is still impacting your team please let us know.
Thank you again for providing valuable feedback to our team!