One is opening a bottle of relish which has already been opened and closed many times before Shabbos. When he screws off the cap of the bottle, the letters that are on the cap are destroyed, as the cap is opened at precisely the spot where the letters are. And when he screws the cap back on, the letters are "recreated" again, which may also be a prohibited form of "writing."
Although it has been written by R' Neustadt here
Contemporary poskim agree that it is forbidden to open bottle caps which are stamped with the date of production, etc., and the letter formation will be broken or erased when unscrewing the bottle cap
I believe he is referring to a case where one is opening the bottle for the first time. Is the case different where the bottle has been opened and closed before, or does it make no difference?