Id find a new supplier.

I have run liquid argon on Titanium with zero issues.  But good gas, as Al has mentioned, is only half the battle.  The rest is everything down stream of the cylinder.  Regulator, fittings, hosing, gaskets, solenoids, etc.  Before I did anything, I'd buy a gallon jug of Snoops leak check from Swagelok, and a spray bottle, and get to checking every connection and line in my system. 

If you don't have an oxygen meter that measures in PPM, now might be a good time to justify one.  Ours has been an absolute work horse and held up very well to three welding engineers who play welding technicians on a daily basis.  We purchased ours from Alpha Omega Instruments Corp. Rhode Island. 

The other route, and I'd not go this way unless you absolutely have to, is to run all of your high pressure cylinders through Matheson NanoChems.  We have 3 cylinder manifolds that go through a NanoChem for all of our mechanized TIG equipment.  They work very well, but their price is very steep.

When I was working in the naval nuclear shop we had similar concerns about argon purity, even with the tightest specifications and best suppliers.

The solution in this case came in part through the installation of a dryer/purifier at each weld station, in addition to our purity alarm systems.

It has been so long that I don't remember the specific equipment vendor even, but by now they probably have improved versions on the market.

I'm not sure what you are using now or if this would even fit your budget, but it is my 2 cents worth.

Not possible in this neck of the woods.

Yes, it's true what you said it could be related equipment in these cases. But the change in weld is immediate upon bottle change. We may use eight T's per month between two welders not counting some purge gas. We'll reject one in twenty five on a good stretch, but then get a scatter of bad ones, maybe three in twenty five. Supplier great guys, swap bad ones for free. I don't want to speculate about their end of things.