It is very weird, the patchiness of the supply issue.
I have no idea why it would be really obvious where i am and not where you are. Probably just down to individual drivers, on particular regular routes, down to who has left and who has stayed in their jobs?
There's absolutely nobody who lives where i do (in the two nearby towns i mean, with one large supermarket and a couple of smaller ones in each town) who hasn't been well aware of the problem for many weeks now. It has become normal to just wait and see, not expect to be able to get all the stuff on yr shopping list and adapt to what is available. Time of day makes no difference either.
Personally I'm not someone who cares deeply about food or needs to find very particular ingredients for my planned meals or anything so am not massively bothered by it but if you did need to get specific stuff on a specific day i imagine you'd be having a bad time.