random pkg "failed checksum from repository" errors

From: Graham Menhennitt <graham_at_menhennitt.com.au>
Date: Tue, 14 Jun 2022 09:23:34 UTC 
I've just installed a 13.1 Release system on AMD64. Trying to install 
some packages:


# pkg install xorg kde5 sddm nvidia-driver-390
Updating FreeBSD repository catalogue...
FreeBSD repository is up to date.
All repositories are up to date.
The following 890 package(s) will be affected (of 0 checked):

New packages to be INSTALLED:
...

[99/890] Fetching llvm13-13.0.1_2.pkg: 100%  159 MiB 179.5kB/s    15:31
pkg: llvm13-13.0.1_2 failed checksum from repository


I then repeat the same command and llvm works correctly but another 
package further on fails with the same error. After a few tries of the 
command everything eventually succeeds. So it appears to be some kind of 
intermittent error.

Does anybody have any suggestions, please.

Thanks,

     Graham