Now this is just a guess nothing sure But since you said after you have replace the PNP switch (but the flashing arrow still coming on) We know the flasing coming frong the PNP selector gear...

So I will do this
1) Put the key in the ingintion turn it to possition 2
do not start the engien..

2) Move your gear select lever from P to all gear apply the foot on the brake
than going back to P

You asked why we doing this .. I think if the PNP switch is not lining up correctly when it is in stall or happend to be a deffective PNP switch hey who know these thing do happend you know..

3) Now turn on the motor cranck the motor if fire on first or second tried than you know it have some thing to do with you PNP swith...

could be also a bad startor brush inside the starter itself.. they do worn out over time....

Now I am not a pro or expert ... just a thought.. try it nothing to lose

good luck... Please let us know what is the end result when you fine out in the end....