Solder balls are not uncommon, and are generally harmless. Since you bought you Pi4's a long distance in time apart they will have been from very different batches, so I don't think that is the problem.ganzgustav22 wrote: ↑Wed Jul 01, 2020 12:42 pmOut of curiosity just opened two brand-new Pi4B 4GB packages (also bought from Reichelt, just a few months later) and it's the same. Multiple solder balls on different places on the PCB.
(Made some close-ups/crops so it's easier to spot them)
Pi4B 4GB 1
Pi4B 4GB 2
I think the problem lies in something in your kiosks blowing the Pi4's up. Presumably something the previous models were not as susceptible to, but still something out of spec somewhere. I think that if you run a Pi4 outside that scenario, on a standard monitor, running whatever software you are using, it won't fail.