I have cleared out my software distribution downloads
Go back and do it again. Empty the entire contents of the software distribution folder.
In order to do this, you will need to stop both the Windows Update Services as well as the Cryptographic Service.
If you still have a Windows.old folder get rid of that as well.
You can do that relatively quickly by using an admin command prompt and typing
cleanmgr /sageset:1
hit enter and check every box
then type
cleanmgr /sagerun:1
hit enter and let it run
Afterwards go back and try the upgrade again.
You should be offered 17774 which is newer than 17771
The reason your post is not receiving more attention is that there are only a few of the members of this forum who actively participate in the insider program.
I myself have only ever experienced the problem you are describing on one previous occasion and that was many months ago on a previous build. I don't even remember which one or how I finally resolved it.
Probably started over with a clean install from an insider ISO
https://www.microsoft.com/en-us/sof...StwNw-74SihbvLfPoS3k74vDzeMw$$$&wa=wsignin1.0