METAR/TAF expiracy calculation wrong
If the METAR/TAF is outdated, e.g. 311200 with current date&time 011200, then the app mistakingly shows its issue time as “in 691h” or similar, depending on actual date & time. So it calculates like if the already outdated one is far far in the future...
Some TAF/METAR issueing stations do not update messages for certain periods, e.g. weekend days etc.
Also, would be great to mark already outdated TAF/METAR (the last one loaded into app) as expired, if it passed its defined validity (1 hour for METAR, for TAF the period specified in its header). So the user indifinitely knows that the message shell not be used.
You can “spy” how it works for example in AviationWeather app...