also a bunch of customers will come in at once, like 10's of customers and they won't stop coming in and it lags my game a lot, and if i satisfy one he won't be able to leave because the others are blocking him and then more come, i fix this by saving and continuing my game
Saving and reloading will purge the non-save file data, yeah - which includes customers
The reason the additional customers are spawning IS NOT LIMITED TO WHAT I'M ABOUT TO SAY.... but what I say below here is DEFINITELY one of the main ways.
Shield Customers currently cause an issue when they "Wait" for the second item, No matter what, if you sell anything to a shield customer, they will cause one more additional customer to spawn, one for every time you repeat this. - These are not intentional spawns, and as a result, other issues associated with them are not necessarily bugs, because the additional customer itself is the bug.
Avoidance can be done by simply dismissing Shield customers right off the bat, and if you accidentally allow two or more customers, it is likely safer to just go ahead and save and reload then and there, rather than wait.
additional as I said, not limited to Shield - There could be some other less obvious things that are triggering additional spawns as well - and while I've never seen it personally, The custom difficulty also has a setting for "Multi-order" which sounds like a customer could ask for two or more items, not necessarily being shield(s) - if this DID occur ever, that customerr too would likely cause another customer, as well. - since it seems tied to the "Waiting"