fire burns forever on non flammable blocks

Issue: Non-flammable blocks that catch on fire in the overworld are not extinguishing themselves.  Eg:  There are dirt blocks near my base that have been on fire for the past three days.

Expected result:  Blocks should extinguish after waiting for a while.

Reproduce:  Set a block on fire (eg: obsidian) in the overworld; can use flint and steel.  Wait a long time; it does not extinguish.

 

Also, blocks in my world are randomly ignite.  That's a bit irritating, but I can deal with it.  Not sure how you can reproduce this.