Why waste your time on all this to again point out that it makes no sense. I know it makes no sense yet I have seen toggling the region to any other one and then back fix similar issues many many times over many years.
Whatever the bug is its been there for a long time, I've never ever been able to piece together the chain of events that leads to the screwup (I suspect MYOB themselves are in the same boat. It is by far the weirdest thing that occurs from time to time). I've seen MYOB spend money screen look correct when recorded (and when opened to edit) but reports show as US with it not allowing me to fix it properly until the region toggle was done.
Again toggling is definitely the correct first step, then you check the individual wage transactions to see if the dates are in line with the a-ok ones, then re-run all the payslips to see if they are now (bizarrely) correct and consistent. If not correct at that point then MYOB Support is next.