Dear all, I'm messaging from the UK on behalf of my 14 yo son, who is an enthusiastic euphonium player! We have recently bought him a new instrument ( Arnold and Sons, AEP-1150). The instrument played well for the first month, but then the first valve began to get 'sticky', and required lubricating with Blue Juice at least every 10 mins of playing time. I've helped my son to meticulously clean the valve pistons and casings (with lint-free cloths). We also checked that the valve guide had not rotated. None of these have helped remedy the situation. It's such a shame, as I really wanted him to enjoy his new instrument! The instrument is under warranty, and I intend to go back to the shop from which we bought it. His teacher thinks that we should give the euphonium a bath, and that the problem is probably some dust getting between valve and casing. However, I'm not so sure that this is the case, as on detailed visual examination I can see no dust. I wonder whether anyone on the forum has any ideas on this? Is it possible that the distance between the edge of the piston and the valve casing wall is too small, and therefore hard to maintain lubrication? I really would appreciate any insight - thank you! (If this post would be better placed somewhere else on the forum, then please let me know)