SRX5K ISSU upgrade failing due to "ERROR: Failed to add junos-vmhost-install-srx-x86-64".

Unable to upgrade SRX5K devices to a version greater than 21.4R3.

If the error "ERROR: Failed to add junos-vmhost-install-srx-x86-64" shows up when using ISSU for an upgrade to a version greater than 21.4R3 then please check the routing engine installed on the nodes using "show chassis hardware" and look for "RE1800x4". If this routing engine is the one installed then you have a RE2 (Routing Engine 2), the latest Junos version for this RE model is 21.4R3 which means that newer versions will only be available for RE3. If you try to push a RE3 (" junos-vmhost-install" image) image on a RE2 then this behavior will be observed.