Okay, I managed to isolate the problem.
Backtest attached. You'll see that there is 1 min left to current bar's close. Set time frame to H1 & the step value to M1 and step forward once. EMA will go through the floor.
There is one more related bug. After you step forward, the last 'tick' comes and the bar closes. Then, the next bar opens, but time remaining on the next bar starts to count down from 4 hours, rather than 1 hour. When that bar closes, next bar shows 30 mins left, which is also wrong.
When you step forward once more (again for M1), then the chart jumps down but there is no bar visible:
![Screenshot 2023-12-04 225541.png](./download/file.php?id=264&sid=174d3a8ae3bcbc33619b47f37ba80517)
- Screenshot 2023-12-04 225541.png (39.89 KiB) Viewed 30711 times
Red arrow shows where current price is.
Only after that bar closes after 30 mins, the next bar becomes visible and counts down from 1 hour:
![Screenshot 2023-12-04 225822.png](./download/file.php?id=265&sid=174d3a8ae3bcbc33619b47f37ba80517)
- Screenshot 2023-12-04 225822.png (34.17 KiB) Viewed 30711 times
Now it looks like a data problem.
![Sad :(](./images/smilies/icon_e_sad.gif)