7 months? If I memory serves me right, 6.4.1 was just released less than two weeks ago.
It is quite possible that the two issues I discovered are regressions in this particular code. I must admit, I did not try any other version of 6.4.
As for specifics, I have GRE tunnels between Local & DMZ controllers that carry a single VLAN. Right after the upgrade from 6.3.1.8 to 6.4.1.0, the healthchecks on those tunnels started failing and Link state stayed Down. Master/Local problem was rather weird - communications between the two were working fine from the Layer3 perspective but Local was complaining that it couldn't contact the master, and Master was having in "SENDING UPDATE" (or something similar) after "wr mem" which forces configuration propagation.