The cluster has been set up for us recently by another party... We have not changed the perl verison since we began using it.

Is there a way we can fix this?

File::Sync is an XS module, changing versions of perl means that such modules are not binary compatible and must be recompiled. You can't copy these things between different versions of perl, that won't work. Did you build modules in another system running a different version of perl and copy them over to this cluster? It looks like File::Sync was built with v5.18. If your supplier maintains the clusters perhaps they've changed something. In the past I've seen OS upgrades cause problems when bumping perl versions. To resolve try a manual build of the module.