When logged in to the Infrastructure Manager (IM):
1. Deactivate the sla_engine (wait until it turns grey)
2. Rt-click and delete the sla_engine probe
3. Then delete the sla_engine folder/directory from the file system.
4. Redeploy the sla_engine v20.4 package from the Primary hub local archive.
Then it should start and run.
You can chose to save off the sla_engine.cfg to refer to the settings but the default settings will work, just check the java min/max values and make sure they are at least 2048/4096 respectively.
The SLA / SLO data is maintained in the backend database tables so there would be no data loss.