If you have a custom indicator and the cTrader platform popups up an error message and tells you that it will be removed from the chart it will be because your code could have some logic that is stuck in an infinite loop and starts to consume all of the machines available memory.
Why does it happen?
Almost 100% of the time the issue is because of a block of code in your indicator that is consuming large amounts of memory RAM or the CPU and this will eventually cause the trading platform or even the PC to freeze. In order to prevent this from happening cTrader has a guardian that monitors indicators that behave this way and if they do it will automatically remove them.
How to fix
The only way to stop this from happening is to look at your own code and identify exactly what part of it could be causing the issue, remember this is not a cTrader issue, but instead your own code design.
If you cannot find any problems, please post your code below and we will investigate for you.