You could use the exit code after trying your MSI install, to fail it only in the case of 1618, or pass only for “good” codes… These would need to come after your ‘wait’ command attempts the msiexec
// Fail only on 1618
continue if {exit code of action <> 1618}
Or
// Success only on good exit codes from msiexec
continue if {exit code of action = 0 or exit code of action = 3010 }