Hi,

The symptoms of this appear to be like the problem described in 
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=223065

It seems https://docs.freebsd.org is chunking content needlessly. This results in  broken downloads with fetch.
The problem is intermittent. It's not happening right now, it was happening a lot yesterday though.

So if one follows the instructions to patch in, for example, https://www.freebsd.org/security/advisories/FreeBSD-EN-22:06.libalias.asc

one first has to get the latest pgpkeys.txt to verify the patch.

But this happened when trying to get the keys:

[...]
# fetch https://docs.freebsd.org/pgpkeys/pgpkeys.txt
pgpkeys.txt                                     4% of 5579 kB  530 kBps  
  00s
fetch: pgpkeys.txt appears to be truncated: 265358/5713861 bytes

# fetch https://docs.freebsd.org/pgpkeys/pgpkeys.txt
pgpkeys.txt                                     3% of 5579 kB  500 kBps  
  28s
fetch: pgpkeys.txt appears to be truncated: 195386/5713861 bytes

# fetch https://docs.freebsd.org/pgpkeys/pgpkeys.txt
pgpkeys.txt                                     4% of 5579 kB  589 kBps  
  21s
fetch: pgpkeys.txt appears to be truncated: 252506/5713861 bytes
[...]

one has to auto-resume with a utility like wget:

[...]
# wget https://docs.freebsd.org/pgpkeys/pgpkeys.txt
--2022-01-19 16:59:41--  https://docs.freebsd.org/pgpkeys/pgpkeys.txt
Resolving docs.freebsd.org (docs.freebsd.org)... 96.47.72.106, 
2610:1c1:1:606c::50:3
Connecting to docs.freebsd.org (docs.freebsd.org)|96.47.72.106|:443... 
connected.
HTTP request sent, awaiting response... 200 OK
Length: 5713861 (5.4M) [text/plain]
Saving to: ‘pgpkeys.txt’

pgpkeys.txt                        3%[=>                                 
                      ] 210.33K   551KB/s    in 0.4s    

2022-01-19 16:59:42 (551 KB/s) - Connection closed at byte 215378. 
Retrying.

--2022-01-19 16:59:43--  (try: 2)  
https://docs.freebsd.org/pgpkeys/pgpkeys.txt
Connecting to docs.freebsd.org (docs.freebsd.org)|96.47.72.106|:443... 
connected.
HTTP request sent, awaiting response... 206 Partial Content
Length: 5713861 (5.4M), 5498483 (5.2M) remaining [text/plain]
Saving to: ‘pgpkeys.txt’

pgpkeys.txt                        7%[++=>                               
                      ] 422.84K   609KB/s    in 0.3s    

2022-01-19 16:59:43 (609 KB/s) - Connection closed at byte 432986. 
Retrying.

--2022-01-19 16:59:45--  (try: 3)  
https://docs.freebsd.org/pgpkeys/pgpkeys.txt
Connecting to docs.freebsd.org (docs.freebsd.org)|96.47.72.106|:443... 
connected.
HTTP request sent, awaiting response... 206 Partial Content
Length: 5713861 (5.4M), 5280875 (5.0M) remaining [text/plain]
Saving to: ‘pgpkeys.txt’

pgpkeys.txt                       11%[++++=>                             
                      ] 639.38K   509KB/s    in 0.4s    

2022-01-19 16:59:46 (509 KB/s) - Connection closed at byte 654726. 
Retrying.

--2022-01-19 16:59:49--  (try: 4)  
https://docs.freebsd.org/pgpkeys/pgpkeys.txt
Connecting to docs.freebsd.org (docs.freebsd.org)|96.47.72.106|:443... 
connected.
HTTP request sent, awaiting response... 206 Partial Content
Length: 5713861 (5.4M), 5059135 (4.8M) remaining [text/plain]
Saving to: ‘pgpkeys.txt’

pgpkeys.txt                      
100%[++++++==================================================>]   5.45M  
4.06MB/s    in 1.2s    

2022-01-19 16:59:51 (4.06 MB/s) - ‘pgpkeys.txt’ saved [5713861/5713861]
[...]