Sorry I don't agree that the tv had an inherent fault.
The fact that you have had it working correctly for nearly two years supports this.
HOWEVER
- where you have a claim is that the product must be of 'reasonable quality' and fit for purpose.
Reasonable quality is defined as what would be expected from a 'reasonable' consumer over a 'reasonable' time period
based on cost of the item (up to a maximum of 6 years or 5 in Scotland).
It would not be reasonable for a tv that cost this much to fail within 22 months.
It is also not 'fit for purpose'
- a tv would be defined as something that produces audio & video.
Furthermore if it has HDMI connections etc then they should be able to produce a higher quality level of video.
If it is stuck in standby this would not be therefore fit for purpose.
Whilst software may not be covered this is not the same as a manufacturer's firmware update.
Firware updates are normally provided by discs or downloadable and transferred via a USB stick.
This is not the same as someone installing faulty software on a PC which conflicts with the operating system (OS).
Stand your ground as your are correct in your assumptions.
If you have any photos of the fault, any Toshiba recommendations etc then these will help but you are in the right.
I'm an ex tv engineer by the way.
I'm a little out of touch with the very latest technology
but firware updates I've installed loads and this should not exclude your SOGA cover.
Good luck and keep us posted either way.