Hey Al-chemist 
This is almost certainly a broken screen protector. Mine looks the same and I know of another FP5 where the screen protector looks like this. If you don’t like these cracks, you can simply replace the screen protector.
If you want to protect your phone from damage in the future, I recommend you buy a phone case for your FP5.
But don’t buy the official case as it doesn’t offer any real protection due to its poor design.
Take a look here: