M18 PRCDAB+ radio teardown problem

I am an electronics engineer and I have this M18 radio in for repair. The radio works from battery but not from mains power, and it won't charge the battery because the mains power is not working. I've been trying to open the unit but , boy this is solid! After taking out 10s of screws, nothing will budge, it's held together very tightly. Can anyone advise how to tear this unit down?

I am an electronics engineer and I have this M18 radio in for repair. The radio works from battery but not from mains power, and it won't charge the battery because the mains power is not working. I've been trying to open the unit but , boy this is solid! After taking out 10s of screws, nothing will budge, it's held together very tightly. Can anyone advise how to tear this unit down?