It seems that it's simply impossible to run too many things in parallel over ADB on a single device. Really weird stuff happening, like completely unrelated shell calls using files created by other shell calls. Switch back to serial implementation.

lib/roles/device/support/sub.js

@@ -5,7 +5,7 @@ var zmq = require('zmq')
 var logger = require('../../../util/logger')
 var wireutil = require('../../../wire/util')
 
-module.exports = syrup()
+module.exports = syrup.serial()
   .dependency(require('./channels'))
   .define(function(options, channels) {
     var log = logger.createLogger('device:support:sub')