Took your advice & tried DD-WRT. The DIR-880L is now 100% useless for me.
DD-WRT could not see the DLNA server at all. I searched & searched. Nothing. So I did a 30-30-30 reset of the router. Reinstalled FW1.07 from the emergency FW page. After that I went to the firmware 1.20B1 which has the DLNA fix. This worked fine before the installation of DD-WRT. I was confused as the router somehow remembered my settings once I got to that firmware.
Now I can't see the DLNA server at all on the DLink official firmware. I'm completely hosed.

I used the GUI to reset to factory defaults & re-set everything up. Still nothing. If I connect my laptop directly to the wifi of the DIR-895L I can see the server without issue. If I connect via the DIR-880L I can only see the smb share (which I don't have setup). The DLNA software (Serviio) can see the laptop, the Xbox X & my Blu-ray player as being active but the devices cannot see the server.
I am extremely frustrated that this issue continues to plague me. I wish there was a media bridge or router out there that would work. I cannot fathom why DLNA is consistently blocked.