I doubt it's the tuner if it's worked sometimes, though it could be, so it's a valid test if you have/can get hold of something else. It's more likely to be the cable or the connection. Those last screenshots show valid (and invalid) muxes, but there's no NetworkID or MuxID, which means your tuner has found nothing whatsoever at that frequency - it can't even recognise it as a carrier. You also now are stuck waiting to scan muxes that can't complete, I suspect, hence the 21 muxes awaiting initial scan: 'map services' won't be available until the scan completes.
What would I do...
1. Check you connections. Unplug it all, plug it all back in, tighten it, test it on another device.
2. Delete the muxes you don't want/need/have near you and restart
3. Trash the whole config and start again with what you've learned - adding the right muxes of the right config from scratch, for example
4. Check support on OpenElec for your tuner (it looks like it was introduced in 3.1? https://github.com/OpenELEC/OpenELEC.tv/issues/2203)
5. Try a different version of OpenElec - with a very different kernel - just in case something's broken in the particular release you're using (go forward to betas or backwards to something else, the kernel is listed in the release notes to every version)
6. Try XBMCBuntu to eliminate Linux support; try Windows as well to eliminate hardware/connection issues
7. Drink heavily or find a wall to shout at
8. If all else fails, try a different stick
EDIT
'ello, 'ello, 'ello... what's all this, then:
https://www.mail-archive.com/linux-media@vger.kernel.org/msg75912.html
>> "Avermedia A835B(1835) only works sporadically"
>> "There is a RF performance issue in the af9033 driver of kernel 3.15. It is no problem in the it913x driver of kernel 3.14.
>> There were some initial sequences not correct after the it913x driver was integrated into af9033 driver."
Sooo, it may well be your stick, in that the driver or firmware may be an issue. There's a discussion there about trying different versions of the firmware and getting different (but still unsatisfactory) results. Openelec 4.0.x (at least) is on kernel 3.14, though, so it could be a red herring - but see what the very latest betas are running and/or what 3.x versions used.