Unable to modify a block from the library

Dear friends,

I opened a block from the Simulink library (3 phase PLL) and I tried to do some modifications. When I tried to delete a block there was a message saying "Attempt to modify link 'power_PLL/PLL/Model'. You can disable this link now and restore later". So, I disabled this link and did the modifications. When I tried to run the simulation there was an error saying "Error in 'power_PLL/PLL': Initialization commands cannot be evaluated. The LinkStatus can be set only for a linked block" I did some digging (tried to unlock the library e.t.c.) but nothing worked. Any idea?

Thanks in advance