Luckily, you're correct JCL.
This 013 error only occurs on specific dates and only in TRADEMODE with StartDate = NOW. From what I've seen, it only happens during the end of a weekend or right after it. Maybe setting a BarMode can solve this issue? I can't test this right now because there's currenly no 013 error / date 0 issue.
I don't believe it's the cause of my main problem. Even without this error I'm not able to close trades from a previous Zorro/MT4 session.
My trading script does return messages like these during the beginning and there is a recent *.trd file in my Data folder, but active trades remain open after exitLong() / exitShort() attempts.
[EUR/USD::L01211] - resumed (66 lots)