There are a few different types of screen door locks that door manufacturers have used.
The most reliable brand is Whitco in security screen door locks, these doors get used a lot & kids have a habit of being rough on the locks.
They don’t last forever & are commonly exposed to rain.
Another upside to the Whitco product is, they are not overpriced & readily available.
Below are the manufactures links for these locks.
Pages will give you extra information about the products.
The general public cannot purchase an individual lock direct from the manufactures.
The 3 way locking doors provide much better security from a physical forced entry point of view, but with our Queensland weather these bolts move out of alignment & need to be adjusted.
Once the bolts & strike plates are adjusted the movement in the property will not affect the 3-way locking bolts as much.
Each house moves a different amount & allowing the adjustment extra room will reduce the alignment problems and your door will operate for many years to come much more reliably.
This is not a difficult job to do & most Locksmiths get calls all the time for this problem.
Generally speaking, the job is a quick fix & the cost is just a service call.