With the oboe assembled, check the small pad cups in between LH fingers 1 and 2 and between fingers 2 and 3 to see if they open when you close RH1 - or with the top joint only, press the upper end of the linkage bar running down the right side of the top joint by the LH main action to free them. If they don't open or are sluggish, check the springs are in position in their respective cradles, check the springs aren't weak or broken, check the keywork is running smoothly on the rod screw, check the keywork isn't binding between the pillars and check the pads aren't sticking. If you are able to take the oboe apart (but only if you know exactly what you're doing), check the toneholes and give them a clean with a cotton bud (Q-tip) dipped in some alcohol (eg. isopropyl).
Does this only happen when your oboe is cold, or all the time (even when up to room temperature)? With just the top joint only, press on the upper part of the linkage bar running down the side to open the Bb and C pads (the small pads in between the LH fingerplates) and check there isn't any water in the toneholes. You can only blow the water out while holding the linkage bar down to release these keys - the problem with conservatoire systems is the Bb and C pads remain closed while the top joint is off, so any water collected in the toneholes has less chance to evaporate (unlike thumbplate or dual system oboes where the top joint Bb and C pads remain open until the thumbplate is held down).
If you don't know what the cause is and have never worked on an oboe before, don't undo or adjust anything as you could make things a lot worse. Your best bet is to take it to an oboe specialist as they will know which screws to adjust and how to set them up so everything works as it should do. Due to the interlinked keywork, they aren't ideal for the novice to take a screwdriver to as it only takes a single adjusting screw incorrectly set to muck the whole instrument up - and there are usually around 20-25 adjusting screws on them.
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