Troubleshooting PW2 (6th Gen) lost collections, online too

[Ma'am-I-Am]

I don't know if this is a PW problem or a Calibre problem.
I was backing up my PW2 using a dedicated Calibre db for this. I had a number of books sideloaded and direct from Amazon, plus articles and pdocs - all sorted into various Collections over the years. My PW storage is tapped out.

Somewhere during this late night messing with Calibre & the PW, I noticed the icon to update metadata on the device, so I highlighted them all and ran the update. Here's the situation now:

Using PW, some Collections show, others don't.
Using PW, the Collections that do show don't have the right number of books.
Using K4PC, all collections on Amazon are visible and complete.
New Collections created since then using PW show as blank names on Amazon, although the number of books added to them via PW is correct.
Items added to the new collections show under that collection, but do not disappear from the main page (I use list view).
I have not tried using K4PC to view those new collections yet. I deregistered it and I have no idea why {flappingly frustrated with self}.

One extra thing that may have contributed to this: The Husband and I use a single account and he registered MY PW2 under his name ages ago. I recently changed the Amazon account email address to one of mine because I wasn't getting certain notifications, etc. When the issue with the collections happened, I changed the account email back to his. This made no difference to the collection problem, i.e. it's still f'd up.

I've been using this PW2 for years so I know about filtering, sorting, all/downloaded. I've restarted more than once, but have not reset or deregistered - I want to avoid that considering the volume I have on the device.

Am I SOL in trying to recover the Collections and their proper contents?!

[Quoth]

Do you have more than one Kindle or app registered on this account? That can break Collections.

Nearly anything can break them. It was malicious of Amazon to change the Kindle so that a PC can't set collections.

[Ma'am-I-Am]

Originally Posted by Quoth

Do you have more than one Kindle or app registered on this account? That can break Collections.

Nearly anything can break them. It was malicious of Amazon to change the Kindle so that a PC can't set collections.

We do, but it was never a problem until I did those 2 things: update metadata and change the email used at Amazon (then back again another day).

[Quoth]

Originally Posted by Ma'am-I-Am

We do, but it was never a problem until I did those 2 things: update metadata and change the email used at Amazon (then back again another day).

Yes, that's the sort of thing that breaks it. Having a PW3 and DXG on same account broke my collections. But I already had an Original Aura H2O then. I bought the PW3 just after the PW4 came out and got poor reviews, just before they sold out.

[Ma'am-I-Am]

I don't question this happened to you. I do need to say that we've had our Kindles (both physical and K4PC) on the same account for at least 10 years with no problem. I screwed it up in some way. Now I either need to fix it - which is why I posted - or I need a definitive answer which explains why I'm f*d and need to accept the mess.