Thanks for the hint Harvey!
I have updated my patch to include your changes, but only applied the second hunk for the following reasons:

Wave_read should not assume any wave format, as it is expected to open a file during initialization. So actually the only missing thing was the assignment of the wave format during the reading of the format chunk.

setparams() in Wave_write already sets the wavformat a few lines later together with the other parameters. So no need to set it twice...

Can you please check if the updated patch works for you?