Hello,
In default the printing floats is disabled in the Mbed OS. You need change project configuration via mbed_app.json file (edit an existing one or create a new one in the root of the project). It could look like here - mbed_app.json example
MbedOS crashed because you probably use printf or any read/write method inside of interrupt. These methods are covered by Mutex so it is not possible to do that like that.
You can change project configuration (same as above) to bare metal profile (No RTOS = no Mutex = no crash) or you need change your code.
BR, Jan