35mm

1. Sometimes it is very responsive, but other times I need to click everything twice to get what I want e.g. track up down, transport buttons etc. Some kind of lag sometimes. Is there a reason or fix for that?

If you open Utilities / AZ Controller - 1 and look at "Last MIDI event" line. Is it lagging as well?
 

 2. Is there any way to program the function buttons - F1 to F8 to trigger custom commands?

In AZ Controller everything is re-programmable. If you open the "Logic" tab and press some buttons, you will see a set of Actions, one with "Shift:+" another with "Shift:-". You can remove them all and replace let say with "Command" action, then select corresponding command
 

 3. Holding Shift and clicking on the strip should give an audible scrub, but seems to crash Sonar and (or) the AlphTrack.

Scrub crashing/bugging Sonar is normally not surface related (most of the time comes from audio drivers).
 

Thanks for the info Azslow3 and thank you for the AZ Controller without which there would be no point in this old device in Sonar now. It seems great so far.
 
I was editing my post when you replied so you would have missed No. 4. I don't think you actually have an AlphTrack so may not be able to comment on that. I probably have to put it down to being old hardware with ageing drivers :)

You are right, I can not directly help with (4). And (1) can be related.
From general experience, check the cable, try to use different USB port and USB (power) related options in BIOS/Windows.
 

I'm trying to install az controller on windows 10 but windows is blocking it. How do I get around that?

OK I installed it via the console run as admin..... and it works woo yay!