Thanks for pointing this out, this sounds strange, I would need to test with a spare card later.
What happens if you go into MyOSMC → Overclocking and change it in there to normal?
I can do that and it stays on normal. Seems there is just a custom setting by default on install.
I also have received my MPEG-2 codec and am happy to report that after a short test, the tv recordings seem fine. Only took about an hour to receive it as well 
Great news on the codec, maybe after some more testing just set the thread to solved.
I will check the Overclock setting issue later.
I have crosschecked on a fresh install and after initial install the config.txt doesn’t include any speed seetings which means the Pi will use defaults.
When you go into overclocking the “custom” setting point to 850 but the normal one point to 900. So my guess is you might have pressed “apply” with the custom setting chosen.
No, fresh install, went into over clock and it was set to 850 as soon as it opened (with the normal option selected and showing on the right).