Hi. This is an FYI success report. I was having multiple problems recording 18 channels simultaneously from a Behringer XR18 mixer with my private ASIO compilation of Audacity 2.3.1. I was getting inconsistent behaviors from Audacity. Sometimes Audacity would crash. Sometimes all four of the “Save Project” options would be grayed out and I would be unable to save the project. Sometimes the recording would save OK, but Audacity would later report a damaged project file. But about half the time, everything would seem to work OK. And sometimes, something (in Windows?) got screwed up as I could not get Audacity to restart without rebooting my PC. I did not report my varied problems as I suspected a simple horsepower problem and I first wanted to compile with the latest Audacity (2.4.2), so I needed to find time in my schedule to do that.
Anyway, I just happened to notice that the Behringer Clock Rate was set to 48kHz (X AIR Edit => Setup => Audio/Midi => Clock Rate). I changed this setting on the XR18 to 44.1kHz, and now I am no longer having any of these difficulties. 