Demonstrating working and non working module change code in rubymotion. Code was verified on rake console.

crashblock.sh

(main)> z.q
Assertion failed: (b != NULL), function rb_vm_block_method_imp, file vm.cpp, line 3000.
*** simulator session ended with error: Error Domain=DTiPhoneSimulatorErrorDomain Code=1 "The simulated application quit." UserInfo=0x100461550 {NSLocalizedDescription=The simulated application quit., DTiPhoneSimulatorUnderlyingErrorCodeKey=-1}
rake aborted!
Command failed with status (1): [DYLD_FRAMEWORK_PATH="/Applications/Xcode.a...]
/Library/RubyMotion/lib/motion/project.rb:101:in `block in <top (required)>'

crashing.rb

mod = Module.new do
  public_class_method :define_method
  def q 
    'q'
  end
end
mod.define_method :r do
  'r'
end
Kernel.const_set 'X', mod

class Y
  include X
end

z = Y.new
z.q
#> q

z.r
# Crash
# Assertion failed: (b != NULL), function rb_vm_block_method_imp, file vm.cpp, line 3000.

working.rb

Module B
  def a
    'a'
  end
end

Class A
include B
end

a = A.new

a.a
#> a

Module B
  def c
    'c'
  end
end

a.c
#> c