Chipboard Flooring Joist Help

[Roasted85]

Hello!

Sorry in advance if this has been posted a hundred times before!

As you will be able to tell i'm new to DIY so all advice welcome please!

Upstairs I have a serious creaky bit of 22mm chipboard flooring.

It's where two pieces of chipboard meet and there is no joist underneath where they join.

I have countersunk and run a handful of 50x8g screws along the chipboard where it does meet the joist but this hasn't helped.

To make matters worse this join runs underneath a wall and into the next room.

I read something online about cutting out the join, but I literally have no idea what to do.

Hope someone can help :D

Thanks.