Makes sens to me, temperature will affect permanent magnets.
I guess I am tracking the events, long time ago I removed this engine hub:

[link=http://www.rcuniverse.com/forum/m_6319985/anchors_6346853/mpage_1/key_/anchor/tm.htm#6346853]removing the BME hub[/link]

I guess this is how I eventually overheat that section, however the engine worked seemingly fine after I removed the hub using the methode described in the above link.
If you see the date that was long time ago.

That can explain a lot of things happening on this engine. I am sure I did not overheat that area, however enough to expand the diameter of the hub to remove it.
The pulling forze was not enough that day to extract the hub I recall.

Now I face the dilema, how can I remove the hub of the new engine without using some heat to remove the hubs?