All day today, even after completely closing the game and Steam, ATC has been giving me odd instructions that dont equate. This were their last instructions for my current flight. “climb and maintain FL210, barometer 29.62” ok…that barometer number felt weird to me but hey they know best right? So I did as instructed. Only once I hit FL210 at 29.62 I get CONSTANT ATC messages saying I am 300’ above/below assigned altitude. At first I thought " I literally did as instructed" so I ignored them, but just now I decided to try something different. I first selected the barometer they specified, then hit and maintained the altitude they specified/ I then played with the barometer to see what was going on. This is where I find their faulty instructions, and the above/below assigned altitude messages stopped. Anyone else encountering this???
The ATC uses 18000ft as transition altitude (the altitude when you switch from the actual pressure you were given to 29.92") Thats why you were not at your assigned altitude. Below 18000ft you will not be called because it is what ATC expects. The bug here is that TA is not the same everywhere but the ATC does not know about it 
Hmmm, ok that makes some sense. I say some because today is the first time I have come across this bug, but IS NOT the first time I have flown over 18000. But I guess i should just go to 29.92 at/above 18000 is what you’re saying from now on?
I mean just the other day I swear ATC would have me switch barometer settings while I was at like 20-30k feet, but now you are making me second guess that lol
I am quite sure about this
Transition altitude and transition flight level - IVAO - International Virtual Aviation Organisation gives a good overview
Yes anytime you reach transition altitude 18000 for US, Europe and some other countries during climb you set it to Standard (STD). Middle East is 13,000 ft. Once you reach the TA on descent you set it back to assigned barometer
Was wondering what STD meant, cause I just KNEW it wasn’t the other meaning! I mean, my common sense drew up the conclusion of standard, but I didn’t know what standard was for. now i do!
Lol, if figured you wouldn’t think the other thing
Reason why you might have not noticed or encountered ATC screaming at you might be because the difference between local and standard pressures were not big enough to trigger it.
I especially love it in Europe when ATC is very upset at all the RYRs, EZYs and KLMs that they are xft above their 10 000ft assigned altitude.
DUUUUUUUUDE, last night ATC was ALL OVER this Brickyard character for like 30 minutes cause he was 20k over intended altitude
It looks like the ATC algorithms don’t "see"your stndard altitude setting and directs you to the height based on your barometer. SO when you do it right and set your barometer at standard when passing the transition altitude then atc begns to give you the order to go up or down, WHen i set it to baro atc stops advising so then it is satisfied with your altitude which is actually wrong. In Europe the transition altitudes differ per country and sometimes per region e.g. in the alps. When you pas transition altitude you have to set your baro to standard when you are climbing when descending you have to set it to barometric. It is al done to garantee that above transition altitude planes fly with the same standard setting and thus avoiding midair colissions. This bug has to be fixed with priority because it is essential to real life flying.