Try calling StopTree on your UBehaviorTreeComponent before calling RunBehaviorTree and see if that helps.
UBehaviorTreeComponent* BTComp = Cast<UBehaviorTreeComponent>(BrainComponent);
if(BTComp) BTComp->StopTree();
bool rtVal = RunBehaviorTree( Owner->GetStateByBehaviorTree( AMonsterBase::EBaseState::Chase ) );
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