What does your vet say?
Could it be a deep seated infection that hasn't been cleared up and is reoccurring? I sometimes use
Surolan ear drops - prescription only - but it's important to complete a full course
One of mine has problem ears - allergy related. The only effective cleaner I've found for him Cleanaural, it dissolves and shifts the wax whereas other cleaners don't touch it. However my vet has recently recommended TrizULTRA+Keto by DermaPet. She uses this on her own dog with problem ears and has said it's making a big difference to his comfort levels.
In between cleaning you can try this (which works for mine)
**Wipe the inner ear flap with a very dilute solution of Hibiscrub - you can just make up a solution and spray it onto a cotton wool pad for convenience
**Lift his ears whilst he's sleeping - let a bit of air in there to keep them dry
**Make sure the ear canal is free of too much hair - I remove some of this and it seems to work
My boy now knows all my "Oh oh she's going medical" signs, and every code word for ears. If he can make himself scarce he will do!! It's worth persevering though :)