Not sure if working as intended, but 2 of the 3 picked in Hard LDoN poofed after 4 and 5 failed attempts. 313 skill. Last one was empty which is also annoying.
Some other things to worry about. SoS will likely be broken if you catch a trap even if you took no damage (AA is supposed to reduce this chance but has never worked on traps that I've experienced before 105), and will be re-broken after an Escape if the trap is still floating in the air, even at more than 30 feet, regardless whether it hits you or not. Most are not marked on Good's maps either so be extra careful sneaking through Miragul's, it is designed to keep everyone out including if not especially sneaky rogues trying to grind through the worst and most pedantic quest line ever designed.