QAF: java.lang.IllegalArgumentException: Key for add operation must be defined

Environment:
QAF
Java: 8
TestNG: 6.10
Appium: 1.18.0-1
IVY
ivy.xml
BDDTestFactory
Android Device: OS 9

On trying to run any scenario on Android device, it is throwing below exception. It works fine on iOS Device & this was working fine even on Android previously.

<dependencies>
    <dependency org="com.qmetry" name="qaf" rev="3.0.0-RC3"/>
    <dependency org="com.qmetry" name="qaf-support" rev="3.0.0-RC3"/>
    <dependency org="com.qmetry" name="qaf-support-ws" rev="3.0.0-RC3"/>
    <dependency org="org.aspectj" name="aspectjtools" rev="1.9.5"/>
    <dependency org="org.aspectj" name="aspectjweaver" rev="1.9.5" />
    <dependency org="ant-contrib" name="ant-contrib" rev="1.0b3"/>
    <dependency org="io.appium" name="java-client" rev="7.3.0"/>
    <dependency org="org.seleniumhq.selenium" name="selenium-java" rev="3.141.59" force="true"/>
</dependencies>

Exception:

java.lang.IllegalArgumentException: Key for add operation must be defined!
	at org.apache.commons.configuration.tree.DefaultExpressionEngine.prepareAdd(DefaultExpressionEngine.java:419)
	at org.apache.commons.configuration.HierarchicalConfiguration.addPropertyDirect(HierarchicalConfiguration.java:383)
	at org.apache.commons.configuration.AbstractHierarchicalFileConfiguration.addPropertyDirect(AbstractHierarchicalFileConfiguration.java:146)
	at com.qmetry.qaf.automation.util.PropertyUtil.addPropertyDirect(PropertyUtil.java:107)
	at org.apache.commons.configuration.AbstractConfiguration.addPropertyValues(AbstractConfiguration.java:422)
	at org.apache.commons.configuration.AbstractConfiguration.copy(AbstractConfiguration.java:1241)
	at com.qmetry.qaf.automation.util.PropertyUtil.loadFile(PropertyUtil.java:215)
	at com.qmetry.qaf.automation.util.PropertyUtil.load(PropertyUtil.java:202)
	at com.qmetry.qaf.automation.core.ConfigurationManager.addBundle(ConfigurationManager.java:193)
	at com.qmetry.qaf.automation.core.ConfigurationManager.addBundle(ConfigurationManager.java:160)
	at com.qmetry.qaf.automation.core.ConfigurationManager$PropertyConfigurationListener.configurationChanged(ConfigurationManager.java:418)
	at org.apache.commons.configuration.event.EventSource.fireEvent(EventSource.java:249)
	at org.apache.commons.configuration.AbstractConfiguration.copy(AbstractConfiguration.java:1247)
	at com.qmetry.qaf.automation.util.PropertyUtil.addAll(PropertyUtil.java:180)
	at com.qmetry.qaf.automation.core.ConfigurationManager.addAll(ConfigurationManager.java:285)
	at com.qmetry.qaf.automation.testng.TestNGTestCase.setupTest(TestNGTestCase.java:80)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:104)
	at org.testng.internal.Invoker.invokeConfigurationMethod(Invoker.java:515)
	at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:217)
	at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:144)
	at org.testng.TestRunner.beforeRun(TestRunner.java:656)
	at org.testng.TestRunner.run(TestRunner.java:624)
	at org.testng.SuiteRunner.runTest(SuiteRunner.java:387)
	at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:382)
	at org.testng.SuiteRunner.privateRun(SuiteRunner.java:340)
	at org.testng.SuiteRunner.run(SuiteRunner.java:289)
	at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
	at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
	at org.testng.TestNG.runSuitesSequentially(TestNG.java:1293)
	at org.testng.TestNG.runSuitesLocally(TestNG.java:1218)
	at org.testng.TestNG.runSuites(TestNG.java:1133)
	at org.testng.TestNG.run(TestNG.java:1104)
	at com.intellij.rt.testng.IDEARemoteTestNG.run(IDEARemoteTestNG.java:66)
	at com.intellij.rt.testng.RemoteTestNGStarter.main(RemoteTestNGStarter.java:109)

This is most probably because of property without key. Check your each property files line by line and remove unnecessary lines. Sometimes it observed that after checkout with merge conflict file containing conflict information that needs to be cleaned up.