3042529 - URLEncoding Error - Not able to delete Synonyms/Stopwords with special characters

Whenever you tried to do a full Solr index, after have modified any synonym or stopword containing special character the indexing fails and the following errors are shown:

Aug 01, 2018 1:58:47 PM org.restlet.engine.log.LogFilter afterHandle
INFO: 2018-08-01 13:58:47 10.18.9.89 - 10.18.9.86 8983 DELETE /solr/schema/analysis/synonyms/en/pay+invoice - 404 - 0 0 http://localhost:8983 Apache-HttpClient/4.4.1 (Java/1.8.0_172)

INFO | jvm 1 | main | 2018/08/01 13:58:47.297 | Caused by: de.hybris.platform.solrfacetsearch.solr.exceptions.SolrRestException
INFO | jvm 1 | main | 2018/08/01 13:58:47.297 | at de.hybris.platform.solrfacetsearch.solr.impl.AbstractSolrSearchProvider.executeHttpDelete(AbstractSolrSearchProvider.java:602) ~[solrfacetsearchserver.jar:?]
INFO | jvm 1 | main | 2018/08/01 13:58:47.297 | at de.hybris.platform.solrfacetsearch.solr.impl.AbstractSolrSearchProvider.exportSynonyms(AbstractSolrSearchProvider.java:314) ~[solrfacetsearchserver.jar:?]
INFO | jvm 1 | main | 2018/08/01 13:58:47.297 | at de.hybris.platform.solrfacetsearch.solr.impl.SolrStandaloneSearchProvider.exportConfig(SolrStandaloneSearchProvider.java:275) ~[solrfacetsearchserver.jar:?]
....
INFO | jvm 1 | main | 2018/08/01 13:58:47.297 | Caused by: de.hybris.platform.solrfacetsearch.solr.exceptions.SolrRestException
INFO | jvm 1 | main | 2018/08/01 13:58:47.297 | at de.hybris.platform.solrfacetsearch.solr.impl.AbstractSolrSearchProvider.executeHttpDelete(AbstractSolrSearchProvider.java:602) ~[solrfacetsearchserver.jar:?]
INFO | jvm 1 | main | 2018/08/01 13:58:47.297 | at de.hybris.platform.solrfacetsearch.solr.impl.AbstractSolrSearchProvider.exportSynonyms(AbstractSolrSearchProvider.java:314) ~[solrfacetsearchserver.jar:?]
INFO | jvm 1 | main | 2018/08/01 13:58:47.297 | at de.hybris.platform.solrfacetsearch.solr.impl.SolrStandaloneSearchProvider.exportConfig(SolrStandaloneSearchProvider.java:275) ~[solrfacetsearchserver.jar:?]

And in Solr console log we see the following:

2018-08-01 13:58:47.191 INFO (qtp1961176822-23) [ x:master_siteone_Product_default] o.a.s.r.RestManager Resource not found for /schema/analysis/synonyms/en/pay invoice, looking for parent: /schema/analysis/synonyms/en
2018-08-01 13:58:47.191 INFO (qtp1961176822-23) [ x:master_siteone_Product_default] o.a.s.r.RestManager Found parent resource /schema/analysis/synonyms/en for child: pay invoice
2018-08-01 13:58:47.191 INFO (qtp1961176822-23) [ x:master_siteone_Product_default] o.a.s.r.RestManager Found ManagedResource [org.apache.solr.rest.schema.analysis.ManagedSynonymFilterFactory$SynonymManager@1adf450b] for /schema/analysis/synonyms/en/pay invoice
2018-08-01 13:58:47.191 INFO (qtp1961176822-23) [ x:master_siteone_Product_default] o.a.s.r.RestManager [master_siteone_Product_default] webapp=/solr path=/schema/analysis/synonyms/en/pay+invoice params={} msg={pay invoice not found in /schema/analysis/synonyms/en} status=404 QTime=0

Solr OnPrem Standalone

404; synonyms; stopwords; special character , KBA , CEC-SCC-COM-SRC-SER , Search and Navigation , Problem