I'm new to these very small compact action cameras, just took mine out for its first time and after about 50mins, it over heated and turned the LCD off, im just wondering if its a common issue with action cameras,  or just this one? i'm also concerned how this will affect the lifespan of the camera, and whether if left longer it would stop recording completely

Any advice much appreciated

I have a 4k dashcam for my car that also gets quite hot. It would seem that working in 4k uses a lot of processing power generating a lot of heat. Presumably all is within acceptable limits.

DJI have certainly acknowledged that they get hot, from the manual:-

Hi, thanks for the inquiry. Aside from the good advice from Aardvark, the Osmo Action can shoot up to 4K, 60fps video at 100 Mbps. The amount of video file data generated in one minute can reach 700 MB. It is inevitable that the camera emits heat when dealing with such a large amount of data in a short time. So it is normal that the device emits heat. However, the Osmo Action pays special attention to this problem. The internal heat dissipation area, such as the heat sink and the lens cover removes heat from the device to ensure the normal operation of the camera, and it is repeatedly tested that the temperature is within a reasonable range. Hope that this would clarify your query. Thank you for your support.