my girl will sometimes go a couple of weeks on the cold side - seemingly for no reason. To the point where I will tell her off when I get her out and I can feel her coldness. She never bloody listens

As long as your hot/cold/ambient temps are reading within the ranges I wouldn't worry too much. A snake will move when they feel like it. Be mindful of when you observe her as well, as the majority of movements happen at night. Several times I've heard a thud at 1am and walked through to see my girl on her hot hide staring out at me as if to say "no - no I didn't just fall out of those branches again!"

What I also have in the tank is a large bit of java root that forms a "bridge/tunnel" between her two hides and I have silk plants draped along the back covering the gap. I think it looks nice but it also gives her something to crawl under to keep in cover between hides

Also as per above comments, if she's recently moved in a good week to 2 weeks leave alone should help her settle in