No Crank issue

[Bdc101]

So I haven't driven the BMW in about two weeks. Usually I leave it on a small battery maintainer that I have, since I haven't been driving it very often. But the last time I drove it 2 weeks ago it started fine after sitting for a few weeks, so I didn't put it on this time.

Get in it to move it this time and put it in the garage. The last time I drove it, it started up just fine but after stopping and starting it again while hot (in a bank drive thru) it sounded like the starter solenoid was failing, and I was hearing the click with no start. Fortunately it started after four or five clicks, and later that day I had no issue starting it again cold. Anyways, was gonna put it in the garage and take the starter out yesterday, but it wouldn't start.

I get out the jumper cables and try to jump it -- but here's the tricky part. When I put the jumper cables on (seeing 14.5 volts at both the battery and the jump terminals under the hood) and I turn the key to start it, it just clicks and all the gauges on the dash start going down with every click.

I did some searching and it looks like this could possibly be the ignition switch causing a problem (perhaps causing my click/no start problem from a few weeks ago, though I recall that sounding different) but other than ordering one of those, what else could I be doing wrong?

Other observations: the cabin lights come on, the dash comes on, and the odo has not been reset as if I had disconnected the battery. I checked codes with my Foxwell NT510 and don't have the EWS/DME synchronization code, or any other codes that seem likely to cause the problem (just a couple for the secondary air system).