I upgrade at release 7.2.0 and the AP stop to reload .
The TAC service recommends to update though my FGT is at 6.4.9.
Evidently, the build FAP_431F-v6-build0185 was bugged..
P.s.: yesterday, 12 May , was released the new one build 6.4.8 ...FAP_431F-v6-build0197-FORTINET... maybe it would fix the bug