Blower motor cycling on and off

I have a Payne Furnace (model# 396JAZ048080AAFA) using a CESO 110018-00 control board and I have two problems that I suspect may be related.

The first is at the start of the heat or cool cycle when the fan starts up. About 50% of the time, the fan comes on for 2-3 seconds, does not reach full speed and requires a "second attempt" to start and reach operating speed.

The second problem is at the end of the heat or cool cycle when the blower motor switches off. 2-3 seconds after stopping, it cycles on and off again for a couple of second and this happens 3-4 times before finally switching off.

Whe I use the manual override, the fan starts and stops without the above problems.

After looking at the circuit diagram, I notice that the heat fan relay seems to be energized via a transistor that get's it's signal from a "time delay circuit".

I have gone about as far as I can with this without testing to compoent level on the controller PCB (which may be beyond my skill level) so I am thinking about changing out the whole controller PCB.

Does it sound as if I am on the right track or do you have any other suggestions?

All comments welcome!

Thanks so much.

Mark