Can an outdated app cause order-execution problems?

Yes, this is a real and fairly common cause of unexpected issues. An outdated app version might not reflect current margin rules, updated lot sizes, revised charge structures, or new compliance requirements that a broker has rolled out through a recent update, which can lead to orders being calculated incorrectly, rejected unexpectedly, or displaying inaccurate estimated charges. Older versions can also have known bugs that a subsequent update specifically fixed, meaning you could be experiencing an issue that’s already been resolved for anyone running the current version. In some cases, a sufficiently outdated app version might even lose connectivity to the broker’s backend entirely if the API or protocol version it relies on has been deprecated. You make it a habit to update the app promptly rather than deferring updates indefinitely, specifically because trading apps aren’t like most other apps where an old version usually still works fine, here it can genuinely affect whether your orders execute correctly.