Possible gearbox problem 2017 1.6 hdi manual

[bulldozer]

Hi everyone , 
Hopefully someone can give some info. I had a coolant pump fail a few days ago, 
I stopped as the warning came up on the screen , stop engine overheat. 
I checked top and bottom of radiator and it was only hot on top. 
I gave it 10 mins and put the internal heater on full and drove off ( no heat from Internal heater) 
Ended up on a tow truck and got a mechanic to change the coolant pump.

I tired to get it into second gear and it felt stuck, Then no reverse , 
I managed to get home using 1st , 3rd and 5th.
Brought to another mechanic the next day , On initial test he could find nothing wrong 
All gears worked fine. He took it for a little spin and then the problem came back.
Various gears hard to get it into gear , some impossible and intermittently sticking in gear.
He has checked the linkage and all seems fine , Any light on this really appreciated

[deejay_xb]

with engine stopped can you engage easily all gears?

[bulldozer]

with engine stopped can you engage easily all gears?

Yes with engine off the lever appears to go into gear , i didnt try push the car as i did it

[deejay_xb]

if it goes easy without engine on then you need to replace clutch/bearing and maybe slave cylinder because it does not disengage properly

[bulldozer]

if it goes easy without engine on then you need to replace clutch/bearing and maybe slave cylinder because it does not disengage properly

Just an update . Mechanics changed the oil in the gearbox and all is back working 
Very weird , I did not expect this to happen , but 1000 km later and no issues

[bulldozer]

with engine stopped can you engage easily all gears?

Yes with engine off the lever appears to go into gear , i didnt try push the car as i did it

Just to update this . The mechanic took the side off the gearbox .
Emptied out the oil and removed a bit of gunk as he called it 
Worked fine ever since