In theory, the clutch system is self adjusting. The release bearing just runs on the clutch and the slave settles to the correct place.
So the only adjustment is the relationship between the pedal movement and the master.
Here it is important that there is just enough free play in the pedal before it contacts the master when the master piston is at full extension out.
If you overdo raising the bite point to the extent of losing the pedal free play and even eating into master piston extension, then you will have the symptoms you describe. You mention the 12mm spanner, you need two different sized spanners, 12mm is for the lock nut to prevent the adjustment slipping, 10mm makes the adjustment. I had fun with this last year.
If there is still a bit of pedal free play, and the clutch is not slipping, then the problem is in the hydraulics, slave or master, or hoses.
You say you’ve bled the system, then the next most easy thing to change is the slave cylinder. But if this is not leaking then it is most likely OK.
If not the slave then maybe the hose to it is weak and bulging, usually more pronounced when the engine is hot.
If not these, then the master!
If you’ve not already done so have a read here. Alas they want might money now.