Monitoring, Management & Location Tracking

What could cause the Cisco terminal server showing up following error messages when connected to the Aruba AP “Excessive modem signal transitions detected on line 72”?

Terminal server : Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), Version 15.1(4)M4, RELEASE SOFTWARE (fc1)
 
 
CISCO terminal server connected to Aruba APs could trigger below errors on the Terminal servers and how we could fix it. 
 
Jul 26 11:51:39 utc: %HWIC_SERIAL-3-LINEFLAP: Excessive modem signal transitions detected on line 72
Jul 26 12:10:49 utc: %HWIC_SERIAL-3-LINEFLAP: Excessive modem signal transitions detected on line 72
Jul 26 12:29:59 utc: %HWIC_SERIAL-3-LINEFLAP: Excessive modem signal transitions detected on line 72
Jul 26 12:49:09 utc: %HWIC_SERIAL-3-LINEFLAP: Excessive modem signal transitions detected on line 72
Jul 26 13:08:19 utc: %HWIC_SERIAL-3-LINEFLAP: Excessive modem signal transitions detected on line 72
Jul 26 13:27:28 utc: %HWIC_SERIAL-3-LINEFLAP: Excessive modem signal transitions detected on line 72
Jul 26 13:46:38 utc: %HWIC_SERIAL-3-LINEFLAP: Excessive modem signal transitions detected on line 72

 
Solution:
 
All the flow control should be closed default for Aruba AP; once we shutdown the flow controller on the terminal server the error messages should go away as we don't support it.