Different versions of Syslog-ng Store Box (SSB) are running different versions of OpenSSL which means libraries between to versions may not match and can cause TLS errors that can lead to logs not being sent, logs queuing on a "downstream" Syslog-ng Store Box, and other numerous issues. By ensuring that the two Syslog-ng Store Boxes (SSB) are on the same version it can be validated that the OpenSSL libraries match and thus the chance for TLS errors is reduced.
Different versions of Syslog-ng Store Box (SSB) have different features, fixes, and defects, thus, issues can arise when the versions do not match. One version of Syslog-ng Store Box (SSB) may be capable of something another Syslog-ng Store Box version is not and thus issues can arise when sending logs. By ensuring the versions match it can be validated that both Syslog-ng Store Boxes (SSB) have matching features and thus the change for issues is reduced.