Existing fires do not spread when fire tick is changed from false to true

Let me see if I understand:

You turned "fire spreads" off so you can light  a lot of trees for a forest fire without the fire catching you.

Then you logged out to turn "fire spreads" back on.

At some stage you increased the tick to 500/s from 20/s.

When you logged in again the fire wouldn't stop burning.

Two things:

Can an X-box handle 500/s? You may be getting an effective lower tick if not.

When you say it burns indefinitely, do you mean you got a bigger fire than you expected which consumes everything in its path, or that trees are burning for an extremely long time?

If it's the latter, I've noticed this too - whether a block extinguishes or not seems to have a random component attached.

Half of the things you said were wrong. Yes I disabled firetick/fire spread in order to start a forest fire via /gamerule dofiretick false. After lighting some trees on fire I once again used /gamerule dofiretick true and then used the command /gamerule randomtickspeed 500 to change from bedrocks default game tick of 1* not 20, which xbox is infact capable of handling. By indefinitely I mean the fire never burned any of the trees down. I then lit some trees on fire while the tick speed was 500 and they burned. Just a bug that needs fixing 

Duplicated, definitely a bug.

Note to reporter:

I was thinking of game tick when you meant random tick.  My error.

After I read your comment, I did some experimentation with this.  Fire will spread at any random tick setting other than 0[Off] with the fire spread rule active.

I think the problem lies with blocks set on fire under the rule condition dofiretick = false retaining this rule condition after the rule gets changed back to "true".  More than just fire would be affected if it were the random tick getting stuck. 

Mojang can sort that out though.

Probably has the same underlying cause as MCPE-130742 and MCPE-101371: fire blocks seem to only update based on scheduling updates at they moment they are first created, and they do not actually receive random ticks or block updates from surrounding blocks.