List-from-OpenPositionsAllSymbols-to-Determine-data-gaps

I am attempting to observe whether a Symbol with a Open Postion was acknowledged each Execute loop to determine if there is gaps in the data.

I am probably not approaching this with best practice, and I am open to alternative suggestions because this is a bit of a headache.

In PreExecute I am a assigning a list of open Postions from OpenPositionsAllSymbols to the variable "manage".
In Execute, every time the symbol has been acknowledged, I remove that Position from "manage" List.
In PostExecute, if "manage" still has a Count > 0, I am deducing that there was not a BarHistory object pertaining to that symbol that was fed to the main loop.

I think my issue stems from my I assigning manage to OpenPositionsAllSymbols, and it is not a clone. I cannot find any understable way to cloning a List if it is not a List of Primitive types.

Any suggestions on how I can approach this?

CODE:

PreExecute()
{
manage = OpenPositionsAllSymbols;
}
Execute(BarHistory bars, int idx)
{
Position p = LastPosition;
if (manage.Exists(x => x.Bars == bars)
{
// HOLD or CLOSE
manage.Remove(p);
}
}
PostExecute()
{
if (manage.Count > 0)
            {
            File.AppendAllText(target, $"\n\nRunaway Trades: ({manage.Count})");
            foreach (Position p in manage)
                {
               File.AppendAllText(target, $"\n\t{p.Bars.Symbol}");
            }
            }
}