Daniel Gross <gross.daniel.p <at> gmail.com> writes: > I already have AMS math and esint packages enabled in Document -> Settings.
I suspect you have "Use AMS math package automatically" checked (and the same for esint). Uncheck the automatic load of AMS math and check "Use AMS math package". That made the difference for me. The automatic versions mean LyX will load the corresponding package if it detects the need for it. Apparently it's not catching that \dddot requires AMS math (and apparently the other formulas in the document are not triggering it either). /Paul
