This is what ePianos have to say about doing a 'soft' reset:

Do a right-click to open the page up in a New Tab.
https://www.epianos.co.uk/how-to-do-a-soft-factory-reset-on-your-keyboard/

The essence of what they say is below.

How to do a ‘soft’ factory reset on your keyboard

Step 1
Make sure your keyboard is powered off.

Step 2
Hold down the key that is furthest to the right.

Step 3
Keep holding the key as the power comes back on

Step 4
When the keyboard has fully loaded up you can release the key. That is the soft reset complete. Get playing, and hopefully, your issue has been resolved.

Click on this LINK below to watch the video .. then click the back-arrow after to get back to this page.
+ Watch the Video

Comment underneath the video:

Chris from ePianos is here showing us how to resolve those troublesome issues like mysteriously changing split-points or shifting fingering styles, that arise from time to time on the Yamaha Tyros keyboard. This is a really easy way to reset certain setting without having to delete any important files. Have any questions? Just leave them in the comments section below or email us on sales@epianos.co.uk or call us on 01295 266788.