I similarly notice that the station missing squawk code also is more likely to miss Ident, although often Ident will show after some cycles. (The other station also misses Ident from time to time.)
Prior knowledge is what this newbie lacks, as evidenced here, there, everywhere , and this lack is why I am here. So, dump1090, as well as aggregator servers need to combine these messages to make the map work. The “other” receiver may be having difficulty receiving/retrieving some messages. Yes, that make sense. Thanks again. (Although consistently missing one particular type over a period of minutes when airwaves are extremely quiet is still unusual.)