Ok, so the final update. It turned out that the issue with the Mygica/August stick was not a reception issue. My box is dual boot with Windows 10 and the channels tuned in fine under Windows. I spent quite a while tinkering with firmware files but nothing worked. In the end, I moved the USB stick to another port. As far as I remember my mobo has 2 types, USB2.0 and USB3.0. Moving the stick did the trick and now, all devices are tuning in channels.
In the interests of helping anyone who may have the same combination of devices on a Linux m/c, these are my observations:
1. The TBS official drivers work great but only if you use a TBS brand tuner device and nothing else. Some TBS drivers are already baked into the kernel, so it would bemuch better to not install the official drivers as they can,(most likely will) prevent other drivers from operating or will remove them.
2. Rolling back to a previous Kernel is not a good way to troubleshoot. In my case, I had TBS official drivers installed, the Kernel had automatically upgraded and I had reinstalled the TBS drivers twice more (until I finally pinned it). Rolling back, did not help me, because the bogey official TBS drivers were still present. Upgrading forward to a clean kernel is a better way to go!
3. Check if your devices are already included in the current kernel, if they are, the chances are that they are tested and verified as working. So first consider that the issue may be something else(firmware files missing for example), before installing media_build because it may not be necessary and is time consuming and may cloud/compound the issue.
4. Some USB devices work better in specific USB ports (Under Linux). Multiple devices on the same USB bus can also cause issues.
5. Ask for help. There are a lot of helpful people, who are happy to assist. :)
6. Troubleshoot one item at a time. Kaffeine is a useful alternative application to test operation of devices and drivers. You can temporarily prevent tvheadend from starting on boot-up, to aid troubleshooting (in case you think it may be causing issues). With:
systemctl disable tvheadend
And use:
systemctl enable tvheadend
to re-enable it (at next boot).
I hope this helps someone else, Thanks again to all who helped me!