Falcon
When you say had an issue with a valve stem being sunk are you sure it's not bent. Should slip up and down in the guide and spin smoothly. When cam is in head it should never be placed down on bench as some of the valves will be depressed and can be bent.
Over shot retainer. Do you mean a cam bearing cap ? Cams can be quite brittle. They don't respond well to being dropped either. When you torque the bolts to hold the cam pulleys make sure to hold the cam by it's hex.
Did the Lisle 36050 tool do a good job? Easy to use when reassembling the collets or a waste of time?
Earlier you mention a collapsed valve spring. What was the go with that? All that stuff needs to be really spot on or it can cause major heart ache. Especially to the wallet.
So, one of my buckets was sitting about 2mm lower than the rest. We, TonyMR2 and I, assumed this was due to a sunken valve spring. I bought the new springs and buckets off TonyMR2 and got stuck into it. I found the valve stem was "stuck" low. I got some decarb spray and gave it a little bit of love and it came loose although still sticky. Continued to work it up and down and lapped it on the head. It now shift just like all the other valves and the bucket seems to be up where it should be, snapping the cam means I haven't been able to measure the gaps yet to be 100% sure on that.
I did this all with the engine in the car so the Lisle 36050 was invaluable. TonyMR2 will hate this but I used a mallet to get them in. Push down hard with one hand to keep it lined up, bit it a bit of a tap with the mallet and it goes on easy peasy. Managed to replaced them all in maybe an hour or so.
As for the cam snapping, Im not really sure what they are called but the 4 retainers that hold the cam in place against the buckets. I picked up number 3 and put it on 4 (rookie mistake but whats done is done).