Neutral safety switch

[rrrs]

Hi, on my '87 300TD got a problem that car would not start in Park, but it starts fine in Neutral; it is not always; usually first thing in the morning while it will be starting fine in Park after it was used that day...
I guess it would be safety switch issue, but would like to check if it might be something else or what is the right procedure to troubleshoot.

PS. Just replaced the bushings on the shifter rod, so it is nice and tight now, but this did not fix/help the problem.