In an annnouncement about today's test launch of a UR-100NUTTH/SS-19 missile, the Ministry of Defense representative mentioned that the Rocket Forces has conducted about 150 launches of this missile so far and only three of these were unsuccessful. The total number of launches probably includes launches of all modifications of the missile. However, it probably does not include the launches during flight tests of the missile. And it is not clear if it takes into account launches of the Rockot and Strela space-launchers (a Rockot launcher failed just a few days ago, on October 8th, during an attempted launch of a Cryosat spacecraft).
All this makes it difficult to compare these data with previously published data on overall rate of success for missile launches or with the data on reliability of the SS-18 missile.