I've never witnessed that behavior and I have tried to reproduce it, lots of fast rights and lefts, casual lefts and rights, hundreds in a row, no problemo.
FYI, on the plan for the signal generator program (eventually) is to add button signals too.
If you want to give that a go, the resistors are cheap insurance, I do have actual, non speculative, first hand experience with cooking a chip by connecting them directly
The pin states may not be in a known state when the chips boot up and they may not boot up perfectly in sequence, or you just forgot what code you had on one of the chips
. so two pins could be in output mode (non-low impedence) and one high and one low and that's all it takes.