How do I delete Backups in Dropbox?

I've read through all these posts; I've checked out the website How to Delete Dropbox Backups ; I'm somewhat capable when it comes to computers; I can definitely follow written instructions - & I'm still stumped in a never-ending failure to delete backups loop.

How we got here:

      Over the years, I've had multiple computers, at work & home. Most have been various WIndows flavors; a few have been Linux machines; & of course there's my Android phone(s). I'm currently down to one Linux Mint Victoria, Budgie Desktop machine. Because of size constraints, all of my Dropbox files are on an external Seagate drive in a directory clearly marked "Dropbox." Although I had downloaded and installed the Dropbox Linux desktop software from the website, I never could quite get it to work correctly, so I've gone back to using InSync to handle my every day file sinking. There's no problem with that.

Now for the problem:

     In checking to ensure that everything had been properly transferred to the new Seagate and was working properly, I found out that all of those old machines were still showing up on my Dropbox Security tab and that  Dropbox Backups shows 4 computers: PC (now shows as unlinked); PC (now showing as linked with last backup earlier this month); Dell G3 Laptop Backup (now showing as unlinked), & PC (4) (now showing as unlinked. The problem is that those 3 unlinked backups still contain a little over 50GB in data. I want to download that data to ensure that I've not missed anything & then erase those backups.

This is where the loop comes in. Every time, even when I click on an empty directory in an unlinked backup & tell it to delete, I get the popup that tells me to tell Dropbox "I don't have access" & then go to Backup Settings. The "I don't have access" link takes me back to the Security tab which already shows that I'm unlinked (now I've even deleted those links) but the Backups are still there & I still can't do anything with them.

I have noticed one issue, the Security Tab never had a Dell G3 Laptop listed, for instance, or a PC(4), all of those old computers were listed according to the name I'd given them.

So, please help get me out of this eternal loop! Thanks