That error can be tricky to troubleshoot - there could be various causes.
What's the monitoring load on this Collector, compared to the other three? These errors can be caused when the Collector is stressed, using high cpu/memory.
Alternatively, the problem can be on the vCenter side - some configuration or permissions error specific to the Clusters/Hosts that this Collector monitors.
I'd advise you open a case with our excellent support team - they will help you get to the root cause of this error.