You mentioned you have had this for a period of time now. TECH214830 covers NetBackup 7.0 – 7.6.0. and does state that bpclntcmd -resync_host_cache process is started by bpcd.
You also mentioned that this issue has repeated around 6 times within a span of 1 year now. That's very few times for 365 days. I believe this may tech note applies.
The one major issue of troubleshooting this is that this is a known intermittent issue that is not very easy to replicate. So much so that it spans that whole NetBackup 7.x line.
We do have an EEB for this issue, but in order to even apply that, you would have to get to 7.5.0.6.