Ever since 1.16 we have noticed an issue we have called "Invisible Fire". This issue is on Bedrock Edition and I have first hand seen it happen on PS4, Xbox One and Switch.

We always play with Fire Spreads set to off

Basically you set fire to a block with a flint and steel and then break the block 'under' the fire.

The fire remains and you can take damage from it when walking through it but the fire is invisible and not rendered.

If you place another (any) block back under the fire it becomes visible again.

You can put the fire out with water buckets when it is both visible and invisible.