In the current released minecraft version of bedrock, Mobile, Xbox, Windows 10, there is a glitch where fire will become invisible, and still produce light and damage when they are on a block and that block becomes filled with air using the /fill command.

Example: 3x3 Packed Ice is placed and fire it lit on top of them. Only the packed ice is cleared using the /fill command and they are filled with air, the fire is still there but invisible.

Edit: It also seems to do this whenever I mine the block that fire is over, not just when the /fill command is used