For months now I have been unable to update the system from 35210. I posted a question here on this forum shortly after the error first occurred - sadly to no avail.
External factors forced me to ignore the problem for a while, until I could find a solution that didn’t involve a fresh reinstall. The system has become woefully slow with what appears to be extremely high levels of disk R/W activity.
I will likely be forced to reinstall, however, before I do that I would be grateful for some level of enlightenment as to the cause - not least that I, and others, might be more able to avoid a repeat of this cluster f**k.
All attempts to update, repair, diagnose using swupd result in the following, rather non-specific, cryptic error message (of which I am unable to find much information on):
Update started
Preparing to update from 35210 to 36420
No packs need to be downloaded
[100%]Bus error
Running swupd diagnose also results in the same bus error with a more than 4000 line list of missing files:
1. Diagnosing version 35210
2. Downloading missing manifests...
3.
4. Checking for missing files
5. -> Missing file: /usr/share/clear/filemap/filemap-ImageMagick
6. -> Missing file: /usr/share/clear/filemap/filemap-Imath
...
134. -> Missing file: /usr/share/clear/filemap/filemap-zstd
135. -> Missing file: /usr/share/clear/filemap/filemap-zstd-bin
136. -> Missing file: /usr/share/clear/optimized-elf/bin000560c7444b3f03df619e463e0e200959893c8f594afc3f46a76d5b1749760c
137. -> Missing file: /usr/share/clear/optimized-elf/bin0058bf295a61706510ea3369ec0ea0607d6dbbdab74fab3783828c7d103e6ac7
...
4056. -> Missing file: /usr/share/clear/optimized-elf/otherffb150920474b05397bb9e0121c1570a78780ddc04e1090807f29ca833f8160a
4057. -> Missing file: /usr/share/clear/optimized-elf/otherfff361aff4f33062e3c8d1781da758c53227ed8133170ee8c25a6066195bf9aa
4058. [100%]
4059.
4060. Checking for corrupt files
4061. Bus error
From the above output it appears swupd expects application specific file data within /usr/share/clear/filemap/ however my directory is completely empty.
Possibly more to the point though are the 4000 or so 64-bit (?) hash-coded files that swupd reports as missing from the /usr/share/clear/optimized-elf/ directory. These files have alphanumeric filenames prefixed with a general file type descriptor; e.g. bin, exec, lib, and other. I have listed the number of missing files for each type below:
../bin000560c7444b3f03df619e463e0e200959893c8f594afc3f46a76d5b1749760c
[470 items]
../exec01217f74019ef311dea5acec68d031e12a38d4fe3e114115f2a4ba615879b691
[222 items]
../lib0020320d7a69fcca34291237cc552a44dbfb592e5bdb1b378eaee7eb03738014
[2551 items]
../other0049a7cd53a145ead44d52c6ce21493c5bf947db214d7f1b99b9b8f7d6eaa8c4
[677 items]
Finally, I also used the Clear Linux live USB to perform a successful hard disk repair of damaged sectors (using GParted) before attempting swupd repair and swupd update - no luck there either…
Again, I would be extremely thankful if someone could help shed some light on this as I’m lost for ideas now 
Cheers