[tor-relays] What is: Channel padding timeout scheduled

[Eddie]

Noticed that one of my relays (OhNoAnotherRelay02) is showing as 
off-line.  Looking at the logs, I see a bunch of these messages:

Oct 18 08:39:16.000 [notice] Channel padding timeout scheduled 143041ms 
in the past.
Oct 18 08:39:21.000 [notice] Channel padding timeout scheduled 156925ms 
in the past.
Oct 18 08:39:24.000 [notice] Channel padding timeout scheduled 168712ms 
in the past.
Oct 18 08:39:25.000 [notice] Channel padding timeout scheduled 166895ms 
in the past.
.
.
.
Oct 18 10:18:48.000 [notice] Channel padding timeout scheduled 194581ms 
in the past.
Oct 18 10:35:22.000 [notice] Channel padding timeout scheduled 216311ms 
in the past.
Oct 18 10:35:30.000 [notice] Channel padding timeout scheduled 224267ms 
in the past.

What's the cause of this.

I used this downtime as an excuse to do a bunch of upgrades and a re-boot.

Cheers.