Clips freeze briefly before transition, every time

Using a MacBook air, new to Shotcut and not super tech savvy. I’m making a video with multiple clips and no matter what I try, each clip will freeze for a fraction of a second before moving on to the next. There are no filters applied to it. I snapped everything together. I switched it to CFR from VFR (shot on iPhone.)

I noticed that when I hit the “hide” icon (next to the “lock track” and “mute”,) the clips run through the next just fine. Of course, I can’t see the now hidden video, but maybe that is a clue or something.

It’s been too many hours on this first video of mine. About to lose my mind. Any help is greatly appreciated. TIA

This is a preview deficiency. Export and view that, and this will not happen.

Thanks I’ll give it a go