Intermittent DHCP issues for clients

[Oli_Herd]

I'm currently in the process of trying to implement Meraki's and after having two in place working fine, sporadically with no logic attached to it, occasionally a client which has previously that day whether it be an hour or more will not get an IP address after authenticating. As mentioned the client could be have been associated not even 10 minutes before have an IP and then showing in the dashboard for its IP will be 0.0.0.0

It doesn't make sense as the client has connected before and this isn't affecting all clients it just seems to be on the odd few it'll cause the issue, then later in the day work absolutely fine. Wireless health for a particular client when it is being experienced is "type='NO DHCP response' associated='false' radio='1' vap='0' yet miraculously will get an IP say ten minutes later.

The setup is using 802.1x for authentication and WPA2-PSK, MR33s. The SSID configured in bridge mode maps to a VLAN which tagged on the switch port separate from what the AP IP is. Fast roaming was enabled but i have since disabled this in the off chance it could be the transition and or caching going from the old Cisco WLC and Aironet APs to the Merakis, but this has not helped. Looking through the event log on a client which is experiencing this the authentication process via the radius server is complete no rejections on that side of it.

I can't quite understand how or why this is happening, as the problem is intermittent rather than being every single time it makes it hard to troubleshoot as i can'f force it. It's causing a delay to being able to implement side wide which is frustrating just like the problem as i can't seem to understand what the root cause is or where it might be happening. Has anyone else come across this issue previously and or have any advice on where to look or configurations that might resolve this?

Firmware version is 25.13

.

To note the 802.1x is working without fault on the old Cisco WLC on this ssid and it will happen on any of the APs within the network not just a particular one.

Thanks

[PhilipDAth]

Have you got the same SSID on any non-Meraki APs?  That will cause a problem if so.

DHCP server isn't running out of IP addresses?

[Oli_Herd]

The SSID is running on the old Cisco WLC, as this is/ should of been a staged roll out the idea is that they will run side by side until all new APs have been installed. Is it likely that them running on two different solutions going to the exact same DC's for DHCP etc is a potential cause? 

There is around 20% of the scope free so its not that, and like i mentioned it is really sporadic as and when it happens. For instance another machine within the same area wont be having this issue.