Unable to find XML-RPC response in what server sent back

Hi,

We suddenly are experiencing some problems with our OpenNebula. New VMs are stuck in pending state.
Even in debug mode we only have this in logs:

Wed Mar 14 15:50:49 2018 [Z0][VM][E]: Exception raised: Unable to find XML-RPC response in what server sent back. Not valid XML. XML parsing failed
Wed Mar 14 15:50:49 2018 [Z0][POOL][E]: Could not retrieve pool info from ONE

So we found this old bug https://dev.opennebula.org/issues/3733
And indeed our vm pool XML is approximatively above 10Mo since a few VM:

MariaDB [opennebula]> select sum(length(body)) from vm_pool;
+-------------------+
| sum(length(body)) |
+-------------------+
|          11702559 |
+-------------------+

So I’ve run some onedb purge-done purge-history, deleted some old VM etc. Now the catalog is about 8Mo and VM aren’t stuck anymore.
How can I make it work on a long term perspective ?

This is with ONE 5.4.8 on CentOS 7

[root] # rpm -qa|grep xml|sort
libxml2-2.9.1-6.el7_2.3.x86_64
libxml2-devel-2.9.1-6.el7_2.3.x86_64
libxml2-python-2.9.1-6.el7_2.3.x86_64
xmlrpc-c-1.32.5-1905.svn2451.el7.x86_64
xmlrpc-c-c++-1.32.5-1905.svn2451.el7.x86_64
xmlrpc-c-client-1.32.5-1905.svn2451.el7.x86_64
xmlrpc-c-client++-1.32.5-1905.svn2451.el7.x86_64

Best regards,
Edouard