Quoted from ccotenj:

thanks for explaining the acronym...
i can tell you that if the cord is appropriately sized (and not an excessive run), the machine has no way of knowing there is an extension cord there (even the resets don't tell you that the machine "knows" the cord is there, it's just "seeing" a power drop that is causing an issue)... an inappropriately sized cord will cause issues, no doubt... many household extension cords are 18 gauge, and that would be a big ask for any type of run... 15 amp circuits in a residential unit are wired with 14 gauge wire... and if they are done according to code, "drops" aren't an issue... if they aren't according to code, and the run is excessive, then you will see a drop (and get resets/issues) regardless of whether there is an extension cord there or not...
similarly, other things on the same circuit can cause issues if they also are high draw units... for example, try firing up a compressor on a circuit that is running something like a vacuum cleaner as well...
but again, none of this is unique to a pinball machine... it's all electricity 101... the device has zero way of telling what wire it's hooked up to... wire is a passive device...
christmas tree lights aren't extension cords, and electricity 101 (again) tells us why you can only hook up so many on one circuit/connected together before you have issues...