Trying to fix windows not being able to install update file KB5005033 - DISM Restore Health source files not found (Error 0x800f081F) -

BITS will always revert to Manual or Manual Trigger. Feel free to set it to Auto or Delayed Auto but a restart will reset it. Ditto wuauserv and to an extent WaaSMedicSvc, but varies by Windows ver. Safest way if you want it to always run is to set to Auto as you have done, and then just accept what happens after that - a reversion by the system to Manual or Manual Trigger. When you say above 'turn off', Manual is not turning it off. In function, it's as good as Auto or Auto Delayed because it will always get triggered on. BTW if ever you want to delete SoftwareDistribution in the Windows folder, first ensure BITS is not running, otherwise you may well find yourself with a BSOD.

Re Silbian above, 3.5 is not installed. That's the solid black square I referred to which means partial - in this case partial means nothing useful installed. You need to get a good old fashioned solid tick in that box and then let wuau do its thing. I have never known it not fix the 'Source not found' error 0x800f081f in DISM once you RestoreHealth. That's not to say it will never not fix it, never say never, but it has always worked for me on many systems over a long period of time.

BTW the stuff I've written above is a little off the topic of KB5005033 - I've addressed specifically the 0x800f081f  'Source/s not found error' in DISM.  But the two are related.  KB5005033, just like a Cumulative Update or two (or three) before it, is a bit of a problem child.  One of the biggest things that will make it fail is the absence of KB4023057.  No KB4023057, no KB5005033.  The problem is that KB4023057 is not available from the MS Update Catalogue for the more recent versions of Win10 - only the older ones. https://www.catalog.update.microsoft.com/Search.aspx?q=kb4023057    And KB4023057 is version specific, even though they all carry the designation KB4023057.  I know, go figure.  So if you have 21H1 or pretty much anything after 1803, you're not going to get KB4023057 from the Update Catalogue.  You'll only get it using wuau.  But ... it's not over yet.  KB4023057 likes to play in the shadows.  Even when wuau has installed it, it won't show in installed Windows Updates (run from admin Cmd Prmpt    wmic qfe list  ). You won't see KB4023057 there even if you've installed it.  You also can't uninstall it, not surprisingly.  But as i said, no KB4023057, no KB5005033.  If you download KB5005033 from the Update Catalogue   https://www.catalog.update.microsoft.com/Search.aspx?q=kb5005033   when you try to install it you'll get an error "This update is not applicable to your computer" which looks very confusing, because it is confusing, because it is applicable to your computer.  This is just MS double talk for "If you don't have KB4023057, you won't be getting KB5005033."  But even when you manage to get KB5005033 installed, the party’s not over, because even though you definitely have it installed - it's showing when you run   wmic qfe list   and when you do a winver you see 'Version 21H1 (OS Build 19043.116' and you know 1165 means KB5005033, wuau might, at a time convenient to itself, just try to download the whole thing, 650+MB, again.  It will return 'Installed successfully'.  Again.  And then a day or two later it might just decide to phone home again and download and install the whole 650+MB all over again.  It's really good fun.

Yep, 'tick' = 'check mark' (never heard that term!). By 'solid' I just meant 'get that sucker in there'! No empty square, no solid black square, just a nice 'check mark'!