In some areas, clock operators are officials and assigned by the local Officials Organization and work on any number of different control panels that operate the scoreboard clocks. If you can't turn off the 1/10 second feature for a clock operator, perhaps you could post some instructions for how to push those 3 buttons in the proper sequence to assist them (and you).
In Georgia, ECOs are officials for varsity games. When I coached from the press box, I would always turn it off if it was on during pregame. Now that I'm on the field, I DID post instructions, taped to the countertop. Admittedly, those instructions were primarily for the dads that were keeping the clock in sub-varsity games, but they are right there, clear enough for anyone to see. Some guys get it no problem, some don't. If they don't, I send one of our assistants from the coaching box to fix it, because it's irritating on the field (constant flashing). I also know if I have to send an assistant coach because the ECO can't read the instructions on how to do it, we should probably keep a close eye on the clock all night, it's probably not the only thing he isn't going to get right.
And experience seems to have nothing to do with quality of keeping the clock. I have seen rookies that were great, and rookies that were awful. One of the worst ECOs we had this year was the president of the association, who was out with an injury. He was too busy watching HOW the officials were doing, and not paying attention to his job. The R had to reset the clock a number of times that night. One time, the R came over to the sideline to tell us to call up there on the radio to give them a reset time. I asked, "Who's up there tonight?" When he told me, I said, "Wait, isn't he president of your association?" R said, "Yeah, you would think he would know better, but he has the attention span of a first grader. I hate when he has our clock. I wish he would heal up and get back on the field."