Bug: ADS gets locked when using block combos on any melee weapon, haven't tested on exalteds.
Step by step to recreate it:
Start a block combo, stop pressing the ADS/block key and keep the melee combo going, stop the combo and the auto ADS will kick in.
It's pretty bothersome having a broken mechanic on melee like that, especially on higher level missions where one misstep gets you outright killed