https://github.com/raspberrypi/pico-sdk/blob/a1438dff1d38bd9c65dbd693f0e5db4b9ae91779/src/rp2_common/hardware_gpio/gpio.c#L283 The gpio_mask is a uint, which is 32 bits. I suspect GPIOs above 31 are initialized incorrectly on RP2350B.