I think some of this has been touched on before but if not here is one possible idea. Since the problem seems to be people buying UAS easily online, local shop etc... and then not receiving any "instruction" in safe operations due to ease of just flying anywhere (don't need help from others to learn to fly it), what about some type of required education training before purchase?

For example, if you want to buy a UAS that is over say 1/2 pound or so (since these problem fliers are using UAS heavier than that), you have to watch (could be online which is available 24/7 via internet) a required course on safe operation. Then when completed you get a certificate which you could show to local shop or list cert number online at store that would allow you to buy a UAS over 1/2 pound. These certs could then be sent to FAA UAS office for tracking (since they already have this department). Could even list serial number of UAS etc...
I think the "know before you fly" is a good idea, but people don't have to look at it, or they may just throw away the paper they are given.
Now would this stop the problem completely, no, but if someone had to complete a small educational requirement (free online), and knew their purchase was going to be "registered" maybe they would take a "pause" before flying irresponsibly. At least it could give them information about flying near airports, interfering with emergency operations etc... and reiterate that there are laws on the books about that now, and if laws are broken, prosecution will happen.
Kids and others could still easily buy the very small UAS without having to go thru this educational step since those smaller UAS don't seem to be involved in these types of unsafe incidents.
Do I like more restrictions etc... "no", but just proposing another way to help protect all of model aviation moving forward, so just an idea.