I’d agree with @RAc. I’ve never encountered such a behavior even though I’ve similar (pretty common) use cases like @Dweb_2. I bet it’s not a stack problem but a driver issue.
Edit: Rethinking about it brings up the question if the client announcing the Rx window somehow misses to receive the complete amount of data stored in it’s socket receive buffer. Then it’s rather a application level protocol issue than a low level driver or TCP stack problem at the device side.
Another indication for an application level problem would be if a close/re-open of the socket restarts the communication with a normal/full sized Rx window.