No matter how I change the config, after client restart it gets overwritten.
Yes, I stopped the agent before making changes.
What exactly are you changing? it is not a setting that is enforced on System Level (Advanced Settings within the BESAdmin tool), is it? Similarly, have you checked that you are not changing a setting that you don’t have an open policy to keep overwriting? Both would cause the exact behaviour you are describing, so best start there…
Once I have be this problem. Me helped this useful advice RHEL Client sometimes ignores besclient.config Try read this I beliv this help you. Good luck.