Filling cracks in ceiling

[Jupiter01]

I've tackled these a number of times over the years and broadly used the following approaches, after some research:
1. paper plasterboard tape bedded in with easifill and then levelled off with further layers of easifill
2. gouged the crack with a screwdriver and then filled and levelled with easifill

I am finding that #2 consistently fails overtime as the crack opens up. I have had much more success with #1 but often have an issue with the tape bubbling.
To add, I have applied diluted PVA as a base coat in both of these scenarios.

Can I please have your advice on this. Here is the latest crack I need to tackle before I paint this bedroom.

 

[Chivas69]

Have you tried sinking a few screws up into the beams to prevent movement of the plasterboard?

 

[Jupiter01]

Have you tried sinking a few screws up into the beams to prevent movement of the plasterboard?

I am planning to but I also have another crack that runs in the opposite direction to the joist. Trying to establish a good approach for these.

 

[Chivas69]

Do they look like the cracks line up where the plasterboard panels meet? Is it a loft above it?

 

[Koolpc]

Rake out cracks. Make holes along the cracks. Insert low expanding foam. Cut off excess when dry, fill sand, repeat...paint.