Incremental mode

Just noticed that with time, grabbing channels every day, some channels of the same provider started having the problem :

[Error   ] Unable to update channel Animal Planet
[Critical] See log file for details
[Critical] Exception.Message: Object reference not set to an instance of an object
[Critical] Exception.StackTrace:   at WGconsole.Program.UpdateChannel (System.String strIndex, WGconsole.ChannelToUpdate Chan, WGconsole.XmlTarget xTarget) [0x00e4d] in <7fc5d76979374a05ad2db534f70a5f2a>:0 
  at WGconsole.Program.ConsoleApplication (System.String[] args) [0x015e6] in <7fc5d76979374a05ad2db534f70a5f2a>:0 
[  Info  ] Existing guide data restored!

The next day the same channel was grabbed again with errors. So I tried "force" using the same guide.xml and all critical errors disappeared !!  Could it be that incremental mode somehow formats strings incorrectly and cannot be readed again by webgrab ? Is it possible that the problem is due to new version of .NET ?