Possible routing issues in a Vlan

Hey all. Hopefully I can get some assistance in here.

We have distribution switches that differ in models, one is a 6880 and the other is a stack of x2 3750-24p. Some end user devices (to include but not limited to virtualized desktop machines and VoIPs) links into FEX Switches that communicates to the 6880 distro, and other end user devices goes into the access switches which communicates to the stack. The issue, since these virtual machines uses one Vlan for services, is that half of end devices having an aging ARP and IP assignments but other half does not. As a Level 1 network tech, I have yet to comprehend complex routing on areas like this but I played around the running-configs.

When I did my show run particularly on interface VlanXXX on the stack, I found this:

interface VlanXXX
ip address xxx.xxx.xxx.xxx / 26
ip helper xxx.xxx.xxx.xxx
ip helper xxx.xxx.xxx.xxx
no ip redirect
no ip proxy-arp
ip ospf xxxx area 0

Same command on 6880, this came out:
interface VlanXXX
ip address xxx.xxx.xxx.xxx / 26
ip helper xxx.xxx.xxx.xxx
ip helper xxx.xxx.xxx.xxx

Out of curiosity, I copied the stack's running-config over to 6880, gave a clear arp-cache interface VlanXXX command on both switches and something good happened. Not only that end devices' MAC address now correctly appears in their respective distribution switches, end devices on the 3750 stack also had their IP assignments started aging, which tells me traffic passes and services are online.

But now, the half within the 6880 does not age.

I'm trying to end this issue by having all customers getting online. Wonder if redditors can help out. ...

Thank you.