[TriLUG] SpamAssassin randomly failing to update?

[Brian via TriLUG]

Hi Smart People,

Frequently but irregularly, I see notices from cron that sa-update 
failed.  sa-update.log looks like this:

channel: SHA1 verification failed, channel failed
01-Jan-2018 04:20:41: SpamAssassin: Update available, but download or 
extract failed
02-Jan-2018 04:11:16: SpamAssassin: Update processed successfully
03-Jan-2018 05:42:52: SpamAssassin: Update processed successfully
04-Jan-2018 04:25:47: SpamAssassin: Update processed successfully
05-Jan-2018 05:41:35: SpamAssassin: Update processed successfully
channel: SHA1 verification failed, channel failed
06-Jan-2018 04:37:11: SpamAssassin: Update available, but download or 
extract failed

As can be seen, two failures are separated by four days of success. 
It's almost always a SHA1 failure; very rarely it's a GPG failure.

Is something nefarious going on over at the SA update server, or is 
there something wrong on my end, or is this normal somehow?

Thanks,
-Brian