Transmission not engaging in reverse

My transmission started acting strange two weeks ago I would say it started when I first did cold start when the transmission was still cool. At first it would not engage into reverse, I would have to sift back into park than into reverse getting it to move. It did that twice so far in two mornings, but not every morning so far.

Than today while I was driving and in drive gear I was accelerating and it felt harsh like the car wasn't even going down the road smooth. It felt like it wasn't moving at first when I stepped on the gas. Then it smoothed out and it drove okay again.

This isn't everyday when shifting to reverse and today just started the problem in drive but eventually smoothed back out again.

I checked the transmission fill level and it was full at hot at idle. But transmission was a bit dirty, but I could still see red, wasn't brown yet, it didn't smell burnt or feel gritty and it felt smooth, didn't find any metal shavings, nothing is leaking underneath.

Do you recommend, dropping the pan to make sure no metal is found and draining with new filter and pan gasket? To have it rebuilt would be unnecessary because it still shifts into gears fine. Could it just be dirty filter?

Transmission was serviced in 2016 at 53,000

Thanks