Airport Express not connecting for Airplay with strong wifi coverage
I am using an Airport Express to as an airplay device for some outdoor speakers. I have my hardware, other than speakers, in a cabinet in my garage, with the speaker wires running to the outdoor area. The wifi network is a multiple access point setup using Unifi equipment and gets 100Mb/s speed in both the outdoor area and the garage near where the Airport express is located. All devices have latest software installed.
When I attempt to connect to the airport express (in the garage) through airplay 2 from the outdoor area it will not work. If I go into the garage it connects and works without an issue. If I move the airport express to the outdoor area it also connects with no issue. both areas use the same wifi network (although likely connecting to different wifi access points)
Based on the troubleshooting, the strength of the internet is not an issue, but the proximity of my iphone to the airport express is. My understanding was that all devices on the same network (assuming strong connections) should work seamlessly. Is there a solution to this problem or do I need to move the airport express closer to the outdoor zone it is controlling.
I have also attempted to set this up using ethernet to the airport express without success. This arrangement creates additional issues on the network. I was able to get this to work with an older software version on the AEx, but that version (7.6.9 I think) did not support Airplay 2.
Thanks in advance for any help!
iPhone 12 Pro