[#8606] - repeated content in tooltips of bar chart x-axis labels

When an x-axis label tooltip is too long, the content is "automatically" repeated 2 times in a bar chart.

jrxml:
<componentElement>
<hc:chart xmlns:hc="http://jaspersoft.com/highcharts" xsi:schemaLocation="http://jaspersoft.com/highcharts http://jaspersoft.com/schema/highcharts.xsd" type="Bar">
<multiAxisData>
<dataAxis axis="Rows">
<axisLevel name="names">
<labelExpression><![CDATA["Level Label expression"]]></labelExpression>
<axisLevelBucket order="None" class="java.lang.String">
<bucketExpression><![CDATA[$F{myTable.first_name}+"<br/>"+$F{myTable.last_name}]]></bucketExpression>
</axisLevelBucket>
</axisLevel>
</dataAxis>
</multiAxisData>
</hc:chart>
</componentElement>

Test result:
(1) X-axis label: (as expected)
(first line)FirstNameVeryLongVer...
(second line)LastNameLongLo...
(2) Mouse moveover an x-axis label to see its tooltip (instead of bar's tooltip):
(firstline)FirstNameVeryLongVeryLong
(secondline)LastNameLongLongLongFirstNameVeryLongVeryLong
(thirdline)LastNameLongLongLong
However, expected:
(firstline)FirstNameVeryLongVeryLong
(secondline)LastNameLongLongLong

Html/svg script in browser:
<text x="135" style="font-size:10px;font-family:Arial;font-weight:bold;width:130px;text-overflow:ellipsis;" text-anchor="end" transform="translate(0,0)" y="59" opacity="1">
<tspan>FirstNameVeryLongVer...</tspan>
<title>FirstNameVeryLongVeryLong
LastNameLongLongLongFirstNameVeryLongVeryLong
LastNameLongLongLong
</title>
<tspan x="135" dy="13">LastNameLongLo...</tspan>
</text>