Issue :
=====
The following message is displayed when inserting more than 2 uBR-MC88V
####3
%IPCOIR-5-CARD_DETECTED: Card type DOCSIS Modem Card (Universal) 8 Down/8 Up (F-connector) with Integrated Up-converter (0x675) in slot 5/0
%UBR7200-3-ENVM_FAN_OVERLOAD: Fan Tray overloaded, fail to support the linecard at slot 5
%UBR7200-3-ENVM_FAN_OVERLOAD: Fan Tray overloaded, fail to support the linecard at slot 6
%OIR-6-REMCARD: Card removed from slot 6, interfaces disabled
Please check the fan tray in the chassis.
####
The issue is expected as the ubr-vxr cannot support the cooling of more than 2 ubr-MC88V with the old FAN assembly
Solution:
========
Install the new fan assembly
MAS-U7246VXR-FAN2
Reference :
=========
http://www.cisco.com/c/en/us/td/docs/cable/cmts/ubr7200/installation/4939sbc.html
Note 
You must use the new MAS-U7246VXR-FAN2 fan tray when the Cisco uBR7246VXR chassis is loaded with four Cisco uBR-MC88V line cards. However, you can load the router with up to two Cisco uBR-MC88V line cards and still use the old MAS-UBR7200-FAN fan tray.