I think there was a similar one with some crazy guy trying to scale the fence for Obama? And maybe even Bush? I dunno, the crazy white house lawn guys seem to happen every 5-6 years.
There is one thing to consider, and that is the fact that since he left office, he has not had the same level of SS protection.
Presidential candidates still do not get the same level of coverage as sitting presidents do, so he still has less protection than he did while in office. But being a very controversial former president with a very real chance of winning again, he may be a bigger target than most "normal" candidates at this stage and they are having trouble keeping up with the threats with the resources they have.
It doesn't help that Trump is not known for patience or planning ahead, so if he insists on doing things like go playing unscheduled rounds of golf, then the SS has to scramble to secure a giant area with lots of bushes, trees, and cover at a moment's notice. There might always be incidents like this. While president, he might have had enough of a protective force that his golf courses were more full-time secured by SS staff with infrared cameras, command centers, well positioned sentries, etc. Even if they want to extend the full POTUS protection to him again (And I think they probably should if they can), it might not be feasible to provide it to the current sitting POTUS, the VPOTUS/Dem Candidate, and the GOP candidate simultaneously with the manpower they have.
