From constantly dealing with messy files, at times the file being parsed maybe the problem, You may wanna check what is there on line 8 in your file handled by <FILE> and see if it is something different from the rest of the lines (It may contain invalid strings hidden somewhere in the line or at the end of the line for example). or check on whether these errors are repeating more often for certain lines over the others and see how that can be fixed/tweaked just in case because the User Agent strings seem to have no standard format to them.
Excellence is an Endeavor of Persistence.
A Year-Old Monk :D .
