Just a suggestion.
Do not strip / rebuild... CosmoreX Coffee has said before and I fully agree. *Why cause problems.
1: *I would run a descaler through the boiler / system as per a standard Service process..
2: *RIGHT product.. You want dissolved scale ... Not flaky scale.. Flakes will catch and jam other things up.
3: *Fill the boiler with clean water and flush the system.. Weaker solution will be still in parts of the system..
4: *Drain boiler via the drain plug. * Fill and drain... Fill and then flush the whole system again
5: *I would pull the head apart afterwards and check the o-rings and restrictor etc
6: *New group seals
7: *Buff and polish outer skin..
Run some bedding in shots.. *Run the steam wands again.... and make sure no chemical smells etc..
Have a coffee... *Or two... *
Keep EM6910 for AM for parts *;)
Enjoy the BZ35 as it will last for years and easy to maintain..
Then when it fails... Step up a a Silvia or Brevile * ;D
Donate BZ35 to Mum2three *;)