Sampling iphone -> op-z, weird results

I tried sampling via the lightning to USB cable today. But I have weird results. I hope someone can help me clarify if I am doing something wrong.
First: created empty patch on op-z 3rd instrument. So it should be sliced samples. Then connected via usb to lightning to iPhone XS. Then went into sample mode. Pressed play for preview. Already weird behavior: if I play music on the iPhone I hear ticks in the sound, 4 per second or so. I adjusted the gain to the lowest setting, to also avoid clipping by loudnesss.
Then: recorded a fragment of music, I think 10 seconds or so. Now the wave form in the sampler looks like this. Tiny area on the left shows sound, the rest is flat. However, all keys produce sound, even though many times it just looks flat between the green and the blue point. (Except for the left most key, which doesn’t look flat). Unfortunately the ticking sounds also are in the sampled recording, so it is totally unusable.

Anyone any clue about what I might be doing wrong?

Try putting the phone in Airplane mode, that should remove the ticking noise.

Thanks for the tip. I tried a second time (without airplane mode by the way) and it worked as it should, also with correct wave forms. I may also have gotten this issue because I had GarageBand open.