This has been discussed on the PC forum, but as I suppose that many PS4 players do not follow that, a warning here seemed appropriate.
There is a bug that was finally acknowledged on the PC last week. It is almost certainly present on the PS4 as well - but people may not have encountered it yet.
The Tyrant hunt is supposed to drop the Bile Drenched Scale (which you need to restore the Chain of Scales from Rank 5 to rank 6).
The code was supposed to prevent it from dropping if you already had a rank 6 Chain, but due to a slight bug, it will not drop if you already have a Chain that has been upgraded to rank 4 or 5.
What this means is that if you have already restored your Chain to rank 4 or higher, you should NOT waste a Tier 3 lure to summon the Tyrant. You will NOT get the Scale.
If you have not yet upgraded the Chain, you are OK - you can spend the lure and have a chance of the Scale dropping.
Feeling demotivated and taking a break from the forums. Have fun, everyone.