gistfile1.txt

using System;
using System.Text.RegularExpressions;

class Test
{
    static void Main()
    {
        string before = @":[email protected] private #timing :\u000314CODEERROR:\u0003 [\u000304X012\u0003] Server time is different than UTC";
        string after = Regex.Replace(before, @"\\u0{3}3\d{0,2}", string.Empty);
        
        Console.WriteLine($"Before: {before}");
        Console.WriteLine($"After: {after}");
    }
}