The Smart-1 5 is not supported to run any code level beyond R77.30. You'll need to replace it with at least a Smart-1 205 or a VM/open server with at least 2 cores and 6GB of RAM, preferably 4+ cores and 10GB+ of RAM.
Your 4800 units are end of engineering support in 2020 and end of all support in 2022 so start planning to replace them.
Would also echo Heiko's comment about converting to simplified VPN mode prior to the upgrade, while traditional VPN mode is supported in R80+ CoreXL will have to be disabled.
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