The suggestions you have received are good ones
The only thing missing is the why…
When a slave or master is not working 100% what occurs is that the clutch does not come fully uncoupled from the flywheel… it drags just slightly… which turns the input shaft in the transmission… which prevents you from going into gear at a stop.
Shut the engine off… and it immediately shifts into gear… proving this theory
The only thing you need to suss out is if your clutch dragging issue is caused by the master… or the slave
In your case you hope its the master as that is the only easily accessible component between the two…
So begin there and see what u get… if it fixes it great… if not… your transmission is coming out… all just to address the slave
Enjoying those “located on the input shaft” clutch slaves? Yea me too… i feel your pain, believe me