There is a really annoying bug on OP-1 that has been reported by several users (including me). Sometimes when you delete takes from a loop, the lines of the neighbouring takes also diseappear, though the audio remains on the tape. The workaround for getting back the control over those takes is to record silence over them.
Here are steps of reproducing this issue.
1. Select a track (let's say T1).
2. Ensure that tape and bpm are synced, so you see the bar markers above tha tape tracks. Move the tape head to a full empty place of two bars. Press the loop in on the start of the first bar (name it P1) press shift + right to move to the next, press loop out. So you created a one bar loop.
3. Record something to the T1 in that loop.
4. Move to P1 again, press shift + right to move to P2, press loop in, press shift + right again to move to the next point (P3), and press loop out. So you created a new loop right after the previous one.
5. Record something to the second loop.
6. Now move to P1 again, press the loop in, press shift + right to move to P2, press loop out. So you created the first loop again.
7. Ensure that you're inside that loop (the first loop). Press shift + lift to delete all takes from the first loop (event though you have only one take on T1). You expect that only the take on T1 will be removed. However the line of the take from the very next loop will also disappear, but you will still hear the recorded audio if you move the tape head to the second loop.
If you're interested in it, you may try to reproduce it. Thanks!