@BrunoH well, couldn’t it maybe possible that you just don’t have a „classic zone 4“. When you would reach your anaerobic threshold (the point when lactate starts raising profoundly and faster that your metabolism could get rid of it) very suddenly and on a relatively low HR level compared to your max HR , the HR would „jump“ from the Zone 3 to 5 (from below or very slowly building up reasonable amounts of lactate to building them up very rapidly) - leaving out Zone 4 completely?
That’s why I like Zonesense and would like to have it as “outer ring” display instead of the HR-Zones, as it’s giving much better feedback here IMO
