I have a Minecraft account on bedrock and me and my friends usually play on my world. We have noticed that invisible fire was present and found out that you could not put it out by doing anything to it in it's invisible state, the only way to put it out is to put a block next or under the invisible fire so that it shows on top of that block face and so you can punch it out. On the server we have firetick turned off. To create the invisible fire all you have to do is light a block on fire and remove any blocks surrounding it except for the block above.