It happens sometimes, the keys get stuck in the blocks and don’t seal the hole untill I hit them. It’s annoying if it happens while playing. Maybe some oil will be enough, so that the block won’t get in the way with the key. In this case is it better almond oil for the wood or lubricating oil for the key?
Shovel as much of any kind of oil in as possible. Really good for keys.
heh heh 
[Seriously, Jem’s yer man. A truly great unsticker. He’ll be along in a minute …]
I’d use key oil… (yep, he’s no imagination)
then have someone fix it, or at least find out how 
Probably not a good idea to put mineral oil onto the wooden parts of the flute, vegetable oil turns gunky and makes keys even stickier.
Best solution is to remove the keys, clean them and the slot. Look in the bottom of the slot, if you see a piece of metal there that the key rubs on oil that. Just a drop will usually do it.
You may find that the springs need to be re-tensioned- be warned they can break.
i cleaned the key and slot, removed oil and gunk, clean the pin too, adjust spring tension if it looks distrressed, applied sandpaper (very fine) to the sides of the key at the axle point (best solution for stubborn keys) and apllied sand paper to the pin if it seems sticky in the hole.
Never put oil into the key block slots, they will make the keys stick. Like Rama said, clean the key ways and light sand them if necessary. I use a flat jewelry file for this.
My boxwood Olwell loves to do this when the humidity changes. Sometimes I just leave the midsection (the C block is the bad boy) out of the humidified box and that’s enough. I’ve also cleaned and slightly filed a block on another flute, and that’s worked a treat. I used 220-grit sandpaper, but I like Jon’s flat jewelry file idea; seems like it would give more precise control. DEFINITELY NO OIL! That would just gum things up further.
Avoid removing any origianl material until you’ve tried all the none destructive treatments. ie: don’t file or sand anything until you’ve got everything nice and clean, checked spring tension , checked that the spring isn’t digging in etc.
Anything you’ve removed by filing or sanding can’t put it back on.
Thanks people, I’ll try to clean it nicely when I have some time 
You might like to try a hard Arkansas silversmith’s stone instead of a file. They come in small triangle and square shapes, and they leave a very smooth finish. And you might like to fully humidify the flute before doing anything permanent.
I’m absolutely with Dom here. Sorry I couldn’t get in on this sooner (as trailed!!!)
I’d remove the offending key(s) clean and polish them with Brasso or metal wadding, clean the key slot and pad-bed with cloth/cotton buds using methylated or surgical spirit to get any oil and other residues away, likewise the face of the pad (assuming it doesn’t need replacing), and closely inspect the spring for any cracks or other signs of metal fatigue or excessive looseness on its rivet. [The commonest cause of sticky keys is actually excessive bore (and external) oiling. Those pad faces and beds need to be clean and dry, NOT to be gunky!] Then reassemble. It is pretty unusual, save maybe sometimes on boxwood flutes, for keys on antiques (unless they are substitutes or have clumsy solder repairs) to be tight in their slots once cleaned up - they are rather more likely to have excessive play! It is also unusual for keys to be too tight on their pivot-pin once properly cleaned, and I too would strongly advise against any use of abrasion unless absolutely certain it is necessary once all other factors have been eliminated.
I might put a tiny drop of key oil in the pivot hole of a block mounted key, but I certainly wouldn’t pour oil down the slot - that’s just asking for gunk-collection, oil straying onto the pad and other undesired possible effects. I also often put a tiny blob of “ultra slick slide grease” on the tip of a spring, especially one with a metal bearing-plate. It is worth checking that any such plate or the wooden floor of the slot if there is no plate have not worn a groove that is stalling the spring’s action - that is about the only thing that should fetch the files out!
Another thing to check for that can cause key-jamming even when all is clean, the spring is properly set for tension and free to work on its working end, is whether the spring is working around on its rivet/screw laterally in use and coming into contact with the sides of the channel in the block. If so, you need to identify the cause(s) of the travel. It may be necessary to try one or all of the following: tightening up the rivet/screw to prevent twisting; twisting the spring to correct its action; filing the tip of the spring to ensure a smooth, rounded, symmetrical bearing surface; filing a guide groove for its tip to prevent lateral travel (dodgy one, that last!).