I am back... Glad to report that, with the help of both this thread and an anonymous IB person, my case has apparently been solved. Backwardation, alanm and others -- I did not have that box checked last Friday. The "Allow triggering outside of regular trading hours" (RTH) box under Configuration - Orders menu.
And you know what -- that was a deliberate, seemingly rational choice on my part, while systematically going through all the TWS menus and options last month, while the TWS User's Guide was opened on another screen. Rationale: I never trade any security "OORTH" for that security. In other words, I interpreted that option -- incorrectly, as it now turns out -- that the "regular trading hours" are security-dependent. How else could one conceivably define "regular trading hours" for what is, after all, a global, "Universal" account?...
Simply put, since IB's clients trade stocks, futures, currencies, etc., in N. America, Europe, Asia, Australia, etc., not sure I understand any relevance of the NYSE regular trading hours to... well, to anything whatsoever other than trading in NYSE-listed securites.
Interestingly, just searched the TWS User's Guide again. The phrase "regular trading hours" appears in it 8 times, but is not defined anywhere. Seems to me IB could save themselves some headaches by including a simple definition there.
Better yet, why not revise that Config - Orders menu item itself to read "Allow triggering outside of regular NYSE trading hours"? (If that's what it is.)
In any case, I'll keep that box checked for now. Good / cheap lesson learned. My immediate takeaways from this thread are:
1. Create Audit Trail -- great idea... done. (Thanks, Bernd.) In fact, should come in handy not just in case of trouble, but every day. I routinely adjust my exits as part of managing the trade (as, I'm sure, many here do)... the ability to review as part of the end-of-day analysis exactly when I put each adjustment through, will be nice to have.
2 Taking a screenshot of TWS at a key moment -- another good idea. Will do. Incidentally, that might also work well for keeping tracking of my exit adjustments, conveniently time-stamped with the TWS clock.
3. Now that I've used TWS for a while and am fairly comfortable with it, I will revisit the TWS User's Guide and re-check every "suspicious" menu option. This time will attempt not to take anything for granted / read between the lines...
And, yes, I remain a fan of IB/TWS, certainly when it comes to speed / power / adaptability of the interface. Now, about those server-resident stop simulations...
Really appreciate everyone's contributions.
late apex