Spit boils at 212°F. Recommended temp for release of Loctite 273 is 250°C (482°F). If Loctite releases around 212°F it didn't cure properly.
Many people don't understand how Loctite works. Like a lot things Loctite brand has changed over the years. Originally it required an active metal (iron and steel are active metals (but not plated)). It needed to pick up an ion from an active metal to work.
Also oily surfaces prevented it from curing properly.
So unless you used the REQUIRED primer to an inactive metal, and cleaned the surfaces free of, oil it was not working the way you thought. This often gave people the sense that they could use it and take things apart with normal tools. If you are using Loctite brand you well could have to heat the parts to a point where you are changing the temper of teh metal.
Over time Loctite changed the formulation. It now is formulated to tolerate oily surfaces and more importantly contains the missing ion. But remember not all products sold as thread locker are up to the new formualtion.
There are places where Loctite Blue (medium strength) is appropriate on a Triumph. The sludge tube plug isn't one of them. Sealant yes, but Loctite locking compound NO!. There were hundreds of thousands of Triumphs (and BSA
for that mater) that ran without selnt of thread locker with out oil leaks or the plug coming loose. In 60 odd years of working on these motors I have never seen one come loose, or a crankcase damaged where on had come loose in the past. What I have seen is numerous broken crankshafts where the break started at the point where the original staking was drilled out. I drill the face of the plug to remove the divot, so I don't recomending adding additional "retaining" divots (stress points) where cracks can start for a very good reason.
As far as heating something to release the Loctite I have seen too many crankshafts that were heated past the point where the journal turned straw color, or to the point where some were dark purple tending toward black. This is America, if some is good more is better.
After seeing what damage people have done with Loctite I am a firm believer you should be required to have a license to buy it, or at least marked for professional use only. Use some ThreeBond or your choice of thread SEALER.