I already submitted a bug report but I'm trying to make it more visible in case it saves you some hassle.
I do most of my testing on a Kindle Fire HD 10" and my devices just recently updated from Fire OS version 18.104.22.168 to 22.214.171.124.
Since then, deployment fails to devices with this OS version - see my bug report for details.
Basically, the device is now running a process with an odd/long user name. This breaks Xamarin's parsing of the output from the ps command.