Oppo 203 & HEO connection issues

[aspaceintime]

I have 2 MinimServer instances, one on my iMac & the other on my Synology NAS. Recently the instance on my iMac has been dropping the connection to my Oppo 203 & HEOS app for my Marantz A7705. I can see the Synology instance and it works as expected. I rebooted my stuff but that has not solved the issue. NOTE: I can see both instances from the NAS front end (DSM) on my iMac and can manipulate both as required. Everything is connected via the 2.4 ghz wireless network. My Oppo 203 is hardwired to my network and it ocassionaly sees the Mac instance of MinimServer but then drops out never to be seen again. The same can be said for the HEOS app that connects to my A7705. Likewise, my iPads and iPhones do the same thing with the iMac instance. The Synology instance is visible and working on HEOS & Oppo 203 and via the iPhone & iPads. This just started happening in the last month. Any suggestions as to where to look would be most welcome. Thanks!