My process definition is the next, just removed the DI declarations. Both human tasks are assigned to the group "engineer" and assigned to the engineers swimlane. I'm struggling with this since a few days.
<?xml version="1.0" encoding="UTF-8"?>
<bpmn2:definitions xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:bpmn2="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:di="http://www.omg.org/spec/DD/20100524/DI" xmlns:tns="http://www.jboss.org/drools" xsi:schemaLocation="http://www.omg.org/spec/BPMN/20100524/MODEL BPMN20.xsd" id="Definitions_1" targetNamespace="http://www.jboss.org/drools">
<bpmn2:process id="swimlaneTest" tns:version="1" tns:packageName="defaultPackage" name="Default Process">
<bpmn2:laneSet id="LaneSet_1">
<bpmn2:lane id="ingenieros" name="engineers">
<bpmn2:flowNodeRef>UserTask_2</bpmn2:flowNodeRef>
<bpmn2:flowNodeRef>UserTask_1</bpmn2:flowNodeRef>
</bpmn2:lane>
</bpmn2:laneSet>
<bpmn2:startEvent id="StartEvent_1">
<bpmn2:outgoing>SequenceFlow_2</bpmn2:outgoing>
</bpmn2:startEvent>
<bpmn2:sequenceFlow id="SequenceFlow_2" tns:priority="1" sourceRef="StartEvent_1" targetRef="UserTask_1"/>
<bpmn2:userTask id="UserTask_2" name="Final Human Task">
<bpmn2:incoming>SequenceFlow_3</bpmn2:incoming>
<bpmn2:outgoing>SequenceFlow_4</bpmn2:outgoing>
<bpmn2:ioSpecification id="_InputOutputSpecification_17">
<bpmn2:dataInput id="_DataInput_92" name="TaskName"/>
<bpmn2:dataInput id="_DataInput_93" name="Priority"/>
<bpmn2:dataInput id="_DataInput_94" name="Comment"/>
<bpmn2:dataInput id="_DataInput_95" name="GroupId"/>
<bpmn2:dataInput id="_DataInput_96" name="Skippable"/>
<bpmn2:dataInput id="_DataInput_97" name="Content"/>
<bpmn2:inputSet id="_InputSet_17" name=" Input Set 17">
<bpmn2:dataInputRefs>_DataInput_92</bpmn2:dataInputRefs>
<bpmn2:dataInputRefs>_DataInput_93</bpmn2:dataInputRefs>
<bpmn2:dataInputRefs>_DataInput_94</bpmn2:dataInputRefs>
<bpmn2:dataInputRefs>_DataInput_95</bpmn2:dataInputRefs>
<bpmn2:dataInputRefs>_DataInput_96</bpmn2:dataInputRefs>
<bpmn2:dataInputRefs>_DataInput_97</bpmn2:dataInputRefs>
</bpmn2:inputSet>
</bpmn2:ioSpecification>
<bpmn2:dataInputAssociation id="_DataInputAssociation_92">
<bpmn2:targetRef>_DataInput_92</bpmn2:targetRef>
<bpmn2:assignment id="Assignment_1">
<bpmn2:from xsi:type="bpmn2:tFormalExpression" id="FormalExpression_3">Final Human Task</bpmn2:from>
<bpmn2:to xsi:type="bpmn2:tFormalExpression" id="FormalExpression_6">_DataInput_92</bpmn2:to>
</bpmn2:assignment>
</bpmn2:dataInputAssociation>
<bpmn2:dataInputAssociation id="_DataInputAssociation_93">
<bpmn2:targetRef>_DataInput_93</bpmn2:targetRef>
</bpmn2:dataInputAssociation>
<bpmn2:dataInputAssociation id="_DataInputAssociation_94">
<bpmn2:targetRef>_DataInput_94</bpmn2:targetRef>
</bpmn2:dataInputAssociation>
<bpmn2:dataInputAssociation id="_DataInputAssociation_95">
<bpmn2:targetRef>_DataInput_95</bpmn2:targetRef>
<bpmn2:assignment id="Assignment_4">
<bpmn2:from xsi:type="bpmn2:tFormalExpression" id="FormalExpression_6">engineer</bpmn2:from>
<bpmn2:to xsi:type="bpmn2:tFormalExpression" id="FormalExpression_7">_DataInput_95</bpmn2:to>
</bpmn2:assignment>
</bpmn2:dataInputAssociation>
<bpmn2:dataInputAssociation id="_DataInputAssociation_96">
<bpmn2:targetRef>_DataInput_96</bpmn2:targetRef>
</bpmn2:dataInputAssociation>
<bpmn2:dataInputAssociation id="_DataInputAssociation_97">
<bpmn2:targetRef>_DataInput_97</bpmn2:targetRef>
</bpmn2:dataInputAssociation>
</bpmn2:userTask>
<bpmn2:sequenceFlow id="SequenceFlow_4" tns:priority="1" name="" sourceRef="UserTask_2" targetRef="EndEvent_1"/>
<bpmn2:endEvent id="EndEvent_1">
<bpmn2:incoming>SequenceFlow_4</bpmn2:incoming>
</bpmn2:endEvent>
<bpmn2:userTask id="UserTask_1" name="First Human Task">
<bpmn2:incoming>SequenceFlow_2</bpmn2:incoming>
<bpmn2:outgoing>SequenceFlow_3</bpmn2:outgoing>
<bpmn2:ioSpecification id="_InputOutputSpecification_16">
<bpmn2:dataInput id="_DataInput_86" name="TaskName"/>
<bpmn2:dataInput id="_DataInput_87" name="Priority"/>
<bpmn2:dataInput id="_DataInput_88" name="Comment"/>
<bpmn2:dataInput id="_DataInput_89" name="GroupId"/>
<bpmn2:dataInput id="_DataInput_90" name="Skippable"/>
<bpmn2:dataInput id="_DataInput_91" name="Content"/>
<bpmn2:inputSet id="_InputSet_16" name=" Input Set 16">
<bpmn2:dataInputRefs>_DataInput_86</bpmn2:dataInputRefs>
<bpmn2:dataInputRefs>_DataInput_87</bpmn2:dataInputRefs>
<bpmn2:dataInputRefs>_DataInput_88</bpmn2:dataInputRefs>
<bpmn2:dataInputRefs>_DataInput_89</bpmn2:dataInputRefs>
<bpmn2:dataInputRefs>_DataInput_90</bpmn2:dataInputRefs>
<bpmn2:dataInputRefs>_DataInput_91</bpmn2:dataInputRefs>
</bpmn2:inputSet>
</bpmn2:ioSpecification>
<bpmn2:dataInputAssociation id="_DataInputAssociation_86">
<bpmn2:targetRef>_DataInput_86</bpmn2:targetRef>
<bpmn2:assignment id="Assignment_2">
<bpmn2:from xsi:type="bpmn2:tFormalExpression" id="FormalExpression_4">First Human Task</bpmn2:from>
<bpmn2:to xsi:type="bpmn2:tFormalExpression" id="FormalExpression_1">_DataInput_86</bpmn2:to>
</bpmn2:assignment>
</bpmn2:dataInputAssociation>
<bpmn2:dataInputAssociation id="_DataInputAssociation_87">
<bpmn2:targetRef>_DataInput_87</bpmn2:targetRef>
</bpmn2:dataInputAssociation>
<bpmn2:dataInputAssociation id="_DataInputAssociation_88">
<bpmn2:targetRef>_DataInput_88</bpmn2:targetRef>
</bpmn2:dataInputAssociation>
<bpmn2:dataInputAssociation id="_DataInputAssociation_89">
<bpmn2:targetRef>_DataInput_89</bpmn2:targetRef>
<bpmn2:assignment id="Assignment_3">
<bpmn2:from xsi:type="bpmn2:tFormalExpression" id="FormalExpression_5">engineer</bpmn2:from>
<bpmn2:to xsi:type="bpmn2:tFormalExpression" id="FormalExpression_2">_DataInput_89</bpmn2:to>
</bpmn2:assignment>
</bpmn2:dataInputAssociation>
<bpmn2:dataInputAssociation id="_DataInputAssociation_90">
<bpmn2:targetRef>_DataInput_90</bpmn2:targetRef>
</bpmn2:dataInputAssociation>
<bpmn2:dataInputAssociation id="_DataInputAssociation_91">
<bpmn2:targetRef>_DataInput_91</bpmn2:targetRef>
</bpmn2:dataInputAssociation>
</bpmn2:userTask>
<bpmn2:sequenceFlow id="SequenceFlow_3" tns:priority="1" sourceRef="UserTask_1" targetRef="UserTask_2"/>
</bpmn2:process>
</bpmn2:definitions>