Log shows warning "SonosFaultInterceptor" on Sonos search

[chrisl]

Problem Description: In general it looks like everything works perfect, but the log file shows me a warning and fills up the whole log file with the same warning. This warning appears each time I start a search inside the Sonos App. I want at least to understand what this means and if this can create trouble in the future. Hope someone can help me. If more information are needed from the logfile please let me know.
Hardware Platform: Ubuntu 16.04.2 inside a Docker Container on a QNAP TS-253 Pro
Troubleshooting Steps: Reinstalled everything. Tried open-jdk 8 as well as Oracle JDK 8 via WebUpd8. The only explanation I have is that subsonic requires the totally outdated open-jdk 7. Does jdk-8 cause the issue?
Playback Application and version: Sonos System - Version: 8.1.1 (build 38946251)
Subsonic Version: 6.1.2 (build 09b0ab) – October 22, 201
Server Version: jetty-6.1.x, java 1.8.0_131, HSQLDB, Linux (54.3 MB / 124.0 MB)
Java Memory Limit: : 3.46 GB
Log file information: :
[2017-11-05 14:03:37,292] WARN SonosFaultInterceptor - Error: org.apache.cxf.interceptor.Fault: For input string: "search-songs"
org.apache.cxf.interceptor.Fault: For input string: "search-songs"
at org.apache.cxf.service.invoker.AbstractInvoker.createFault(AbstractInvoker.java:155)
at org.apache.cxf.jaxws.AbstractJAXWSMethodInvoker.createFault(AbstractJAXWSMethodInvoker.java:86)
at org.apache.cxf.service.invoker.AbstractInvoker.invoke(AbstractInvoker.java:121)
...
Caused by: java.lang.NumberFormatException: For input string: "search-songs"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:580)
at java.lang.Integer.parseInt(Integer.java:615)
at net.sourceforge.subsonic.service.SonosService.getExtendedMetadata(SonosService.java:296)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
...

[chrisl]

No idea? This is really messing up the errorlog. Nearly every action done in the Sonos App produces a similar warning:

[27.11.17 19:24:20 UTC] WARN SonosFaultInterceptor Error: org.apache.cxf.interceptor.Fault: For input string: "albumlist:alphabetical"
[27.11.17 19:24:45 UTC] WARN SonosFaultInterceptor Error: org.apache.cxf.interceptor.Fault: For input string: "albumlist:starred"
[27.11.17 19:25:02 UTC] WARN SonosFaultInterceptor Error: org.apache.cxf.interceptor.Fault: For input string: "decade:2000"
[27.11.17 19:25:04 UTC] WARN SonosFaultInterceptor Error: org.apache.cxf.interceptor.Fault: For input string: "albumlist:decade"
[27.11.17 19:27:14 UTC] WARN SonosFaultInterceptor Error: org.apache.cxf.interceptor.Fault: For input string: "starred-songs"

To be honest to me this looks like a very obvious bug, something is passing an alphabetical string to a method which requires a number inside. I can't imagine that I'm the only person with this warning...