[Xiaomi Mi A2 Lite Questions & Answers] fishpepper:
See the log above that...

Mine fails because of a mismatch of the system partition hash:

02-28 14:26:35.434 2187 2187 I update_engine: [0228/142635.434222:INFO:delta_performer.cc(374)] Opening /dev/block/bootdevice/by-name/system_a partition without O_DSYNC
02-28 14:26:35.435 2187 2187 I update_engine: [0228/142635.435373:INFO:delta_performer.cc(126)] Caching writes.
02-28 14:26:35.435 2187 2187 I update_engine: [0228/142635.435467:INFO:delta_performer.cc(386)] Applying 4096 operations to partition "system"
02-28 14:26:35.517 2187 2187 E update_engine: [0228/142635.517729:ERROR:delta_performer.cc(990)] The hash of the source data on disk for this operation doesn't match the expected value. This could mean that the delta update payload was targeted for another version, or that the source partition was modified after it was installed, for example, by mounting a filesystem.
02-28 14:26:35.518 2187 2187 E update_engine: [0228/142635.518263:ERROR:delta_performer.cc(995)] Expected: sha256|hex = 51B4F9C76BCC42890BFE311CBA6A52AABD2D70179AA0FAAC0CBEB5641026AB40
02-28 14:26:35.518 2187 2187 E update_engine: [0228/142635.518442:ERROR:delta_performer.cc(998)] Calculated: sha256|hex = 4C44721343DB8284773D6EDFC7C29A9C56126509774D4D26716AC4BA4D2DF4A4

Now I need to figure out why... Seems like something modified the system partition.

The previous OTA worked fine. Since then I installed adaway and the nova launcher... I will investigate further.

---------- Post added at 10:19 AM ---------- Previous post was at 09:59 AM ----------

It seems like i found the culprit... The system partition was mounted writable once... When I installed adaway.

Listing the files in the system partition a:

ls -al mountpoint_sys_a/etc/
total 1660
drwxr-xr-x 21 root root 4096 2019-02-28 16:50 .
drwxr-xr-x 15 root root 4096 2008-12-31 17:00 ..
-rw-r--r-- 1 root root 193171 2008-12-31 17:00 NOTICE.xml.gz
-rw-r--r-- 1 root root 1895 2008-12-31 17:00 SVIConfig.xml
-rw-r--r-- 1 root root 715499 2008-12-31 17:00 apns-conf.xml
-rw-r--r-- 1 root root 5668 2008-12-31 17:00 audio_effects.conf
drwxr-xr-x 2 root root 4096 2008-12-31 17:00 bluetooth
-rw-r--r-- 1 root root 77653 2008-12-31 17:00 boot-image.prof
drwxr-xr-x 2 root root 4096 2008-12-31 17:00 bpf
-rw-r--r-- 1 root root 4476 2008-12-31 17:00 cdma_call_conf.xml
-rw-r--r-- 1 root root 991232 2008-12-31 17:00 cdrom_install.iso
-rw-r--r-- 1 root root 1045 2008-12-31 17:00 clatd.conf
drwxr-xr-x 2 root root 4096 2008-12-31 17:00 default-permissions
-rw-r--r-- 1 root root 6062 2008-12-31 17:00 dirty-image-objects
drwxr-xr-x 2 root root 4096 2008-12-31 17:00 dpm
-rw-r--r-- 1 root root 24398 2008-12-31 17:00 event-log-tags
drwxr-xr-x 3 root root 4096 2008-12-31 17:00 firmware
-rw-r--r-- 1 root root 29926 2008-12-31 17:00 fonts.xml
-r--r--r-- 1 root root 120 2008-12-31 17:00 fs_config_dirs
-r--r--r-- 1 root root 1256 2008-12-31 17:00 fs_config_files
-rw-r--r-- 1 root root 3221 2008-12-31 17:00 gamedwhitelist.xml
drwxr-xr-x 2 root root 4096 2008-12-31 17:00 hostapd
-rw-r--r-- 1 root root 33 2019-02-28 16:50 hosts
drwxr-xr-x 2 root root 4096 2008-12-31 17:00 init
-rw-r--r-- 1 root root 13838 2008-12-31 17:00 ld.config.vndk_lite.txt
-rw-r--r-- 1 root root 289 2008-12-31 17:00 llndk.libraries.28.txt

Notice the modified date of etc hosts... :(