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:
go into survival mode and drink 8:00 fire resistance potion
go into a lava lake in the nether and completely submerge yourself
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
after testing this in 1.15.2 it looks like the fire only stays on for 15-20 sec. when i opened this bug report it was there for a few minutes, maybe it was lag. changing to creative mode takes the fire away instantly btw