I cannot install update KB5009557 (Windows Server 2019, Version 1809, Build 17763.1339) as it fails with error code 0x800f0986.
Both, online update and WSUS, are not successful.
I read several discussions about this error but first of all I would like to understand the error code. The only information I found is a support article from Microsoft where 0x800f0986 is described as
0x800f0986 PSFX_E_APPLY_FORWARD_DELTA_FAILED Applying forward delta failed
I have no idea what Applying forward delta failed means.
So can anybody explain to me what error code 0x800f0986 actually stands for?
Best Answer
This message should only apply to express updates, not full size updates. It means that during the process of hydrating the partial file with forward deltas, it failed. Usually due to corruption or missing files. A simple test may be to download and try to install the full file update.
https://docs.microsoft.com/en-us/windows/deployment/update/psfxwhitepaper