error: java.lang.NoSuchMethodException

[FransZappa]

Tried your suggested workaround, restarted Qnap NAS HS251. Minimserver icon is on the homepage and the JAVA warnings have not appeared. Minimwatch icon however is yellow, should be green, tried restarting Minimserver: no change. This is what the log says:

MinimWatch 0.8.3 update 44, Copyright © 2012-2016 Simon Nash. All rights reserved.
Java™ SE Runtime Environment (build 1.8.0_111-b14)
Java HotSpot™ Client VM (build 25.111-b14, mixed mode, sharing)
Platform default charset is windows-1252

So this is still not update 94 I guess?

Well... as I am explaining the current state of things Minimwatch has some good news and turned green: YES.
Kazoo seems to be up and running and found the main room and working properly.
Lumin needed a little push: it seems to be using a new music library which oddly has the same name as the old one but needs to be chosen in the set-up (it now displays twice MinimserverMyName but one is online and one is offline).
Maybe this info is useful for other users who experience the same issue.

Thank you very much for your help Simon and sorry that I called you Colin in the confusion of things - strange effect this all had on my mindset, must be the reason.