I gave myself an 8:00 fire resistance potion and completely submerged myself in a nether lava lake for about 2-3 minutes. after coming out on land I saw that I was still on fire for a good 30 seconds afterward and it did not go away until I switched to creative mode. taking off the fire resistance with milk caused me to take damage from the fire.

Reproduce:

1. go into survival mode and drink 8:00 fire resistance potion
2. go into a lava lake in the nether and completely submerge yourself
3. emerge from the lava and go onto land, you should see yourself on remaining on fire for longer than expected.

expectation: I stop being on fire after a few seconds, like normal

actual: fire remained on my character for longer than what lava usually does, for longer than 30seconds + and did not go away until I went into creative mode. 

Edit: see comment below, i tested this in 1.15.2 and it looks like it might not be a problem anymore, i mightve been lagging really hard when i opened this report