Transmission grinding

Hi I have a kubota b1400 diesel 4wd I have been noticing an issue
With the transmission grinding when changing gear clutch and brake
Fully depressed it hapens a lot but not all the time often it even
Happens when changing pto gears and even sometimes engaging 4wd
Maybe a clutch problem although when I depress the clutch it all seems
To work proper

It's been doing it since last year not long after I bought
It. Even though it's fairly normal for an old tractor
To grind occasionally I think it happens just
A bit too often