+++ This bug was initially created as a clone of Bug #2016460 +++

Description of problem:
STF 1.3 configured to monitor multiple OSP 16 clouds with out-of-the-box configuration (i.e. by following the official documentation [1]).

The container sg-core of the ceil-meter Smart Gateway fails on regularly on incoming messages with the following errors:

> $ oc logs -f default-tst-ceil-meter-smartgateway-5698bb44dc-4z4vs
> [...]
> 2021-10-21 08:45:20 [DEBUG] failed handling message [error: ceilometer.OsloSchema.Request: OsloMessage: readEscapedChar: invalid escape char after \, error found in #10 byte of ...|ephemeral\|..., bigger context ...|us\": 1, \"ram\": 1024, \"disk\": 40, \"ephemeral\|..., handler: ceilometer-metrics[socket]]
> 2021-10-21 08:45:20 [DEBUG] failed handling message [error: ceilometer.OsloSchema.Request: OsloMessage: readStringSlowPath: unexpected end of input, error found in #10 byte of ...|"vcpus\": |..., bigger context ...|": \"11\", \"name\": \"std.cpu1ram1\", \"vcpus\": |..., handler: ceilometer-metrics[socket]]
> [...]

Full log output is attached, with "dumpMessages" enabled in the SG configuration for increased verbosity.


Actual results:
Not exhaustive, but what has been observed so far:
- some metrics (e.g. cpu_ceilometer) are missing for some overcloud compute nodes in Prometheus/Grafana, resulting in some dashboards (e.g. Virtual Machine dashboard) to work partially (incomplete lists of projects and VMs).

Expected results:
All the metrics/events of all the overcloud compute nodes can be seen in Prometheus/Grafana.