Those are v4l dvb calls from what I can see - so the errors are coming from the dvb OS subsystem rather than tvheadend. The question is why...
From your comments, you've looked at unloading and reloading the modules as you go to suspend... as well as the OE interface, though, you can edit the specific scripts. That would allow you to do some testing from the command line as well (i.e. run the scripts to simulate standby/resume).
You can see the script kicking in here in your log:
Feb 15 22:29:13 openelec user.notice Boot: ### running addon sleep script /storage/.xbmc/addons/service.multimedia.tvheadend/sleep.d/tvheadend.power (suspend)... ###
and
Feb 15 22:29:37 openelec user.notice Boot: ### running addon sleep script /storage/.xbmc/addons/service.multimedia.tvheadend/sleep.d/tvheadend.power (resume)... ###
Does debug logging tell you any more, either in XBMC or tvheadend?
What does the tvheadend web interface look like after resume - is that available, what does the adapter status say, does it look like the adapters are there (so it's an XBMC/addon problem) or not (so it's an OS problem)?
What happens if you manually restart tvheadend again after the system is fully up (in case it's a firmware/module reload issue - timing - tvheadend/XBMC being ready before the tuner has restarted properly)?
I run tvh on a separate system, so I can't really do any testing for you.
I suppose you could try the OE beta with or without the updated tvheadend (3.9) addon, see if that's any better.