Hi Claire,
This can be a problem! If your hair is naturally soft in texture, not sure if yours is but I'm guessing so, then this problem can occur when your hair is too clean and slippery. Using product is key, this aides hold and provides heat protection.
If your hair is coloured it can lead to uneven porosity, which can then mean the mousse you are using to hold the curl is being absorbed by the hair unevenly. I would apply your curling product on dry hair; this gives much more strength and hold. I would opt for a thickening spray and not a mousse - Bumble and Bumble sell one that’s the best on the market. When applying the product make sure it’s even paying particular attention to the areas where the curl is normally placed on your hair, and then dry it in.
When tonging - after you take the tong out pin the curl up till it cools down, this can hold the bend better.
Try all of this on not super clean hair!
