0x800705b4 Update Hangs, Update Troubleshoot Hangs, sfc /scannow Hangs

Hi, some history please (so often omitted by posters):
- when did you last successfully update this PC? (I.e. how new is this problem, noting you're on 1909).
- have you done anything specific to block Windows Update to stay on 1909?

If you look at your Update History (screenshot please) that will show which update (or feature update- upgrade) is failing.

Error 0x05B4 is a timeout error. The error code is most likely related to Windows Defender
https://answers.microsoft.com/en-us/...8-9b008f20da5b

Try step 4 here and report the result:
How to fix Windows Update error 0x800705b4 on Windows 10

However the other symptoms suggest some basic checks are needed.

Turning to SFC /SCANNOW hanging, please run

chkdsk c: /scan
from an admin command prompt and post the summary (not all) result.

Please also download and run Hard Disk Sentinel (trial) - SSDs too- and post the result like this:

Thanks. I note there is no indication of any failure in your Update History.
How have you tried to perform an update?

FWIW you haven't advised the outcome of the simple check in Step 4 of the link I posted.

Have you applied any tweaks or used any 3rd party utilities to make changes to O/S settings or services or to disable Windows Update?

If so, please advise what.

If none:
As your disk is ok, and you have plenty of free space, but there are several unusual but rather basic symptoms, I suggest the simplest option is to attempt an in-place upgrade repair install of your build which keeps all progs and data like any upgrade. (Tutorial available or simplified instructions can be provided if unfamiliar with this).

For this you will need a 1909 iso file (freely downloadable, tutorial available), or even a bootable 1909 installation disk. If you have either of these, you can use them.

'SSDs too' - HARD DISK Sentinel checks SSDs too despite its name.

Ok, I'll assume you mean you checked the state of the services are as shown in that article.

To get a 1909 iso file, one way is to use the Heidoc iso downloader (free) as per the tutorial on downloading a Win 10 iso file.
You need to choose carefully to make sure you get the correct one for your PC - the base language needs to match.

Download that, rt click it.
Click Mount (available by default)
Open the new drive letter in f. explorer
Double click setup.exe - follow the prompts.
Best to choose NOT to accept updates- if WU is operational you could be offered an upgrade.

What's your current build number (winver) and what does your Update History show?

You're not up to date

- gets a variety of opinions from resetting Windows Update, to a bug, to just wait a bit.

Responding to the above will show what's missing.

N.B. with Windows major builds - and even some updates- don't be in a huge rush to update. Hang back and let others feel the pain.

E.g. I kept this on 1903, missing out on MS messing up search when changing it through a feature update, and several updates, and only recently updated to 20H2 missing a couple of other problems. To me, 20H2 is a downgrade. Cortana can't even be used to set reminders now- that's only via Calendar. And my reminders I'd set were lost. I had one GUI issue I had to solve by redoing a theme in Settings (very unobvious). And I couldn't access my other 1903 PC on my network any more - another unexpected simple fix required. Oh, and valid search syntax in file explorer is no longer highlighted in blue- a very useful guide for this partially documented feature.

Advantages? Hmm.... well... ...er....

KB4535680 Security update for Secure Boot DBX - Jan. 12
was Jan 12
KB5003169 Cumulative Update for Windows 10 v1909 18363.1556 - May 11
was May 11 and gives you 18363.1556

Note that 1909 is at end of service on May 11, 2021 for devices running Home, Pro, so the question will be when you are offered a feature update (upgrade).