Thanks for your responses. In fact, the piano is brand new (bought new in May). But at the time of this recording, it had never been tuned, except at the factory (and at the vendor's but I'm not sure about this...). Moreover, the recording conditions may not be optimal. I recorded with an H2 standing on a chair besides me, with the lid closed. Now it has just been tuned, and it sounds much better. I'll post more recordings later. I'll have it voiced soon, as well.
Back to the sonata, it's true that the lyrical sections are slower than the rest, and this is more or less intentional. In fact, I prefer those sections not too fast, they are more lyrical that way, I think. On the contrary, I like the arpeggios and other sections fast. But maybe there should be less difference between the tempi. My teacher always insisted that the tempo should always remain the same. As a result, I was often blamed for playing like a robot. I even failed the 8th year exam for that reason. Years later, I now give myself more freedom with the tempo and other things, trying to play more naturally. I guess I have to find a compromise between the two...
Cheers,
R.