Intermittent name resolution issues

Hi,

I have 3 Orbi RBx50 models running V2.1.4.10 software.  I get intermittent results when trying to access computers on my local network.  For example, one minute this will work...

> ping mycomputer.local
PING mycomputer.local (11.11.11.171): 56 data bytes
64 bytes from 11.11.11.171: icmp_seq=0 ttl=64 time=17.972 ms
64 bytes from 11.11.11.171: icmp_seq=1 ttl=64 time=15.377 ms
64 bytes from 11.11.11.171: icmp_seq=2 ttl=64 time=9.852 ms

but a minute later, I'll try the same and get...

> ping mycomputer.local
ping: cannot resolve mycomputer.local: Unknown host

I'm not sure what to try.  I have Xfinity and my LAN is setup for DHCP on 11.11.11.1-.254 subnet.  Any thoughts on why my name resolution might have intermittent issue?