Hi, I had similar issues. You should definitely check the transmission fluid and also inspect the clutch pads. Sometimes it's just wear and tear.
I recommend looking into the service manual for detailed diagrams. I found it very helpful when I was troubleshooting my 4500 model.
You might also want to check if the hydraulic system is functioning properly. I had a leakage that caused similar problems.
Make sure you are using the correct type of transmission fluid. My mechanic pointed out that I was using the wrong one which affected the clutch performance.