The uncorrectable rear camber was exactly the problem I had. One of my rear upper control arms was bad too, so I replaced both of those.

Regarding a "second look," you may find videos on how to apply a jack to the swing arm, allowing you to see if there is excessive play. I tried to do that without a lift, and without fabricating a special jack attachment (some very creative solutions to this on this forum), and was unsuccessful. So I proceeded anyway with disassembly, and sure enough my ball joints were shot. Practically disintegrating - but there's nowhere for them to go, so they end up being just really too loose.

As I recall from my pre-repair research, the problem with the failed ball joints is not so much that it makes camber too negative - it is that when you get on the gas, the loose ball joint allows the wheel to move significantly in a way that really tears up the inner corner of the tires.

And if my budget (what's that? ;-) ) for my suspension overhaul had been $70, those two ball joints would have been the only things to replace, and this was at ~170k miles. And the next thing I would buy (or rent/borrow), knowing what I know now, would be the BMW-specific ball joint press tool.

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2001 X5 3.0i, 203k miles, AT, owned since 2014