It has been said before. Intermittent symptoms are the most difficult to diagnose.
Basically, if it don't happen when in the mechanics hands, then how can they diagnose it?????
I agree with tacojoel. You've let problems slide for way too long. Now, you are faced with a series of troubles that easily domino onto each other.
This is precisely why I have replaced BOTH cv axles when only one showed signs of failure. And front wheel bearings. And inner/outer tie rods. And rotors/pads/calipers. Yes, the cost is more, but I know those components are good for another 100 Kmiles. In all total, my spend was below $1000.
Stepping over dollars to pick up pennies is not a successful path.
axles were only noticed bad when i got under to change oil and filter and saw a big messy... it was a fast one for sure
thot it was engine oil at first from leaky valve cover gasket draining in the back but it was not that at all