During an ERG workout this morning I got unexpected results when pushing the plus button to extend my interval time.
After hitting the + several times the workout ended at the end of the regular interval but the graph showed that the interval had not ended.
After increasing the resistance to try to match what I had been doing, the interval ended and returned my level back down, which I looped through a couple of times trying to continue at a harder level.
If you look at the activity, you can see at the end of the intervals, I’m frantically pushing buttons trying to raise the wattage as it tries to reduce my wattage. 
https://app.trainerday.com/activities/68c2d0503dd5e7cb22cf34e8
Thanks for taking a look.