Plex cannot connect to HDHomerun

Are you having two interfaces active on the same IP net?

Jun 29, 2018 11:53:12.554 [0x7fa0e7bff700] DEBUG - NetworkService: Browsing on interface 192.168.0.86 on broadcast address 239.255.255.250 (index: 0)
Jun 29, 2018 11:53:12.554 [0x7fa0e7bff700] DEBUG - NetworkService: Browsing on interface 192.168.0.84 on broadcast address 239.255.255.250 (index: 1)

If so, look at Q21 in the QNAP FAQ