Here are recovery.logs for freshly installed LineageOS 16.0 (current build) with its own encryption …
Decryption fail … https://pastebin.com/y0BtS5uW
Decryption success … https://pastebin.com/m50RtbLF
I don’t find a time relevance with 16.0 now … I got decryption to work 1 time with waiting, but now it fails every time regardless of how long I wait with entering the password.
And whether I just reboot to recovery or really turn off/on the phone doesn’t make a difference either.