[Nextant] solr shutdown after a while

Solr is closing after a while of using nextant.

System:
lastest Nextcloud
Nextant 1.0.6
Solr 6.5.0
Ubuntu 16.04 LTS

Has anyone the same issue?

Lars:
Solr.log

2017-04-10 18:07:07.297 INFO  (searcherExecutor-7-thread-1-processing-x:nextant) [   x:nextant] o.a.s.c.SolrCore [nextant] Registered new searcher Searcher@9dee163[nextant] main{ExitableDirectoryReader(UninvertingDirectoryReader())}
2017-04-10 18:07:07.418 INFO  (qtp846063400-12) [   x:nextant] o.a.s.u.UpdateLog Could not find max version in index or recent updates, using new clock 1564315617767456768
2017-04-10 18:07:07.439 INFO  (qtp846063400-12) [   x:nextant] o.a.s.s.HttpSolrCall [admin] webapp=null path=/admin/cores params={name=nextant&action=CREATE&instanceDir=nextant&wt=json} status=0 QTime=2145
2017-04-13 10:31:25.680 INFO  (qtp846063400-16) [   ] o.a.s.s.HttpSolrCall [admin] webapp=null path=/admin/info/system params={wt=json} status=0 QTime=1006
2017-04-13 10:31:26.211 INFO  (qtp846063400-18) [   ] o.a.s.s.HttpSolrCall [admin] webapp=null path=/admin/info/system params={wt=json} status=0 QTime=36
2017-04-13 10:31:26.906 INFO  (qtp846063400-19) [   ] o.a.s.s.HttpSolrCall [admin] webapp=null path=/admin/cores params={core=nextant&action=STATUS&wt=json} status=0 QTime=655
2017-04-13 10:33:31.743 INFO  (ShutdownMonitor) [   ] o.a.s.c.CoreContainer Shutting down CoreContainer instance=1010856212
2017-04-13 10:33:48.027 INFO  (coreCloseExecutor-12-thread-1) [   x:nextant] o.a.s.c.SolrCore [nextant]  CLOSING SolrCore org.apache.solr.core.SolrCore@79ed1be9
2017-04-13 10:33:48.693 INFO  (coreCloseExecutor-12-thread-1) [   x:nextant] o.a.s.m.SolrMetricManager Closing metric reporters for: solr.core.nextant
2017-04-13 10:33:48.799 INFO  (ShutdownMonitor) [   ] o.a.s.m.SolrMetricManager Closing metric reporters for: solr.node