As i wrote, the risk is only very small (as is the chance of winning a million by gambling), but out of my experience it does exist. Latest example was the introduction of the IoT blade that totally messed up an SMB cluster (that had later to be reconstructed manually) after manual upgrade by the customer ☹️
So my suggestion is to roll out new firmware versions manually and test it first on only one GW. If you can not test it without much risk i would wait some time until the gravest bugs have been fixed or the version is broadly accepted in the field and has proven its worth.
This is not only about SMB firmware - remember the Jumbo Takes whose download was disabled after feedback revealed (a) serious bug(s) ? I also would not suggest to install a new plain-vanilla version but instead wait at least for the first junbo take. This is all software and will contain errors / bugs, as is just natural with all man-made things. Only "AI" makes more mistakes 😉
CCSP - CCSE / CCTE / CTPS / CCME / CCSM Elite / SMB Specialist