You are absolutely correct: that was it! In fact, the ILS frequency was not even filled in at all when creating a flight from Salt Lake City Intl. (KLSC) to Denver Intl. (KDEN) in the flight planner (including having selected runway 07 ILS for Denver, with a “direct” approach - I am speaking of the “world map” where you select your departure, arrival, IFR flight and all that). That is, with the stock A320neo.
I had to hastily manually enter the frequency myself just before the landing (which, yes, adds to realism I guess - but was unexpected that it wasn’t already entered in the FMC by the flight planner - after all, “ILS 07” was entered in the FMC already, it was just the frequency (111.55 in this case) missing).
Anyway, this time I also actually experienced a “crash to desktop”, just after touchdown in Denver Intl., when “looking up at the ceiling” (by pressing keys CTRL + 8), in order to adjust the landing lights etc. - boom.
Oh well… better luck next time 