Are you talking about a LOT of citrus falling or do you have a bored, nosey neighbor spying on you and reporting to your HOA every time a fruit drops? Or are these self thinning, tiny, small fruit?
Lemons will drop when they are ripe, however my Arizona Sweet oranges and pink grapefruit don't even want to be pulled off when they are beyond ripe. Yes, a mature orange and/or a grapefruit will drop occasionally. Very occasionally.
Just another reason never to buy in an HOA.

Our trees drop fruit a couple of times ... the tiny green ones drop right after fruit set. It's barely noticeable

the annoying fruit drop is when the fruit is ripe: if you don't strip the tree of all the fruit than, they will drop for a period of several months.

So, when they are ripe, instead of trying to use the tree for a storage device, pick them all.

Low moisture and hot winds in early summer can cause fruit drop. It can be compounded by too little water - make sure you are watering deep and more often than you did in the spring.

Thanks for the replies. Harold, I suspect that it may be in large part a problem of neighbors with too much time on their hands. I'm not there at the moment, so I don't know if it's one or two fruits, or a veritable avalanche. I only know that this hasn't come up before, so I'm annoyedly thinking it's someone being overly fussy - although they're worried about "vermin."