:blush2: sorry i should have specified that i'm storing in 'safe' containers.
It's a known bug in the game, just need a way to 'drain' my armourer skill back below the point where i can repair to above 100% as although 'drain skill armourer' does indeed drain the skill (according to the stats) it does NOT remove the perks/abilities gained at expert level (75)
Sorry-- as you noted, there's no way to lose the perk once you've gained it. You can drain your armorer skill back below 75, but the perk has already been recorded and there's no way to get the game to unrecord it.
It's a shame too, since you can't repair items to exactly 100%, then just leave off there. :shrug:
If you're looking for an easy way to make items safe to store-- take anything you want to store to a smith. Have one item in your inventory that's below 100% (if you don't have one, the easiest thing to do is buy a cheap bow and fire it at a target-- one shot should be enough to drop it to 99%). Have the smith repair your gear and choose "Repair All." You'll only be charged for the one item that's below 100%, but when s/he's done, every item in your inventory will be at 100%.