Very strange. I am not able to recreate this behaviour. If you delete the time offset, then you will need to refresh the merge file. It is possible the views are out of sync depending on when the offset was created.
When you set an offset, LogViewPlus re-parses the file applying the offset. The actual data is modified and the application has no concept of "real" time, so it's very strange that the wrong time is shown in a correctly sorted grid.
It might help if you could send a screenshot.