Strange processing behavior while uploading CSV file using Hot Folder import

I followed the instruction from the below wiki post

https://wiki.hybris.com/display/forum/hot+folder+error+file

and extended AbstractImpexRunnerTask and override the processFile method which sends an email on error during CSV processing. I am trying to upload a Category CSV file with an error. Below CSV has additional ';' in the first line.

 bs-lorealbrandcasting123;L'Oreal Casting Creme;;;L'Oreal Casting Creme;;
 bs-lorealbrandabsolue;L'Oreal Mousse Absolue;L'Oreal Mousse Absolue;;

Impex Header

 <bean id="batchMicroSiteCategoryConverter" class="de.hybris.platform.acceleratorservices.dataimport.batch.converter.impl.DefaultImpexConverter">
         <property name="header">
             <value>#{defaultImpexCategoryHeader}
                 #Insert Categories
                 INSERT_UPDATE MicrositeCategory;code[unique=true];name[lang=$lang];description[lang=$lang];allowedPrincipals(uid)[default='customergroup'];$catalogVersion                  
             </value> 
         </property>
         <property name="impexRow">
             <value>;{+0};{1};{2};;;</value>  
         </property>
     </bean>

Q.1 - Uploading this file generates an error on line 1 and inserts the second category but it does not call my class which extends AbstractImpexRunnerTask.

 <int:service-activator input-channel="batchFilesTranHeader" output-channel="batchFilesImp" ref="batchHeaderRunnerTask"
         method="execute" />
     <bean id="batchHeaderRunnerTask" class="com.superdrug.core.dataimport.batch.task.AbstractCSVUploadImpexRunnerTask">
         <lookup-method name="getImportService" bean="importService" />  
         <lookup-method name="getImportConfig" bean="importConfig" />
         <property name="hostUrl" value="#{hybrisProperties['website.hybris.http']}" /> 
     </bean>    

Q2 - If I reverse the two lines in CSV file as below there are no errors generated and it does call my class which extends AbstractImpexRunnerTask and inserts both the categories.

 bs-lorealbrandabsolue;L'Oreal Mousse Absolue;L'Oreal Mousse Absolue;;
 bs-lorealbrandcasting123;L'Oreal Casting Creme;;;L'Oreal Casting Creme;;

This is very strange behavior and I am not able to understand what is causing this.. If anyone can throw some light on this it will be really helpful.