My MIDI controller won't stay connected to my iPhone 15

I recently started playing keyboards for this band. I only own MIDI controllers, not standalone keyboards, and I didn't want to have to bring a laptop every time we do a gig or a rehearsal, so I got this little USB-C hub so I can connect a MIDI controller to my iPhone, along with an audio output and a power source. I've found some synth apps that sound great, but there's one big problem: All I have to do is barely touch my iPhone, and it will suddenly lose its connection to my MIDI keyboard. Sometimes the sounds goes out too, but usually I just loose MIDI. At this point, I have to disconnect and reconnect my keyboard to get it to work again. Actually, I've noticed that the GarageBand app recovers more gracefully than other synth apps I've been using -- it just stops responding for a few seconds and then it reconnects, without me having to physically disconnect and reconnect my keyboard. But I don't like the sounds in GarageBand as well as other synth apps, plus a lot of GB's keyboard sounds have this annoying echo effect that can't be turned off.

But at any rate, even in GB, this connectivity issue makes it unusable in a live setting, and I don't understand why it's happening. Is this a common problem? The only thing I can think of is that there's something wrong with the USB-C hub, but it is brand new. In fact I even did a little experiment to see if there's anything wrong with it -- it has an SD card reader, so I tried playing some audio files directly from an SD card while slightly jostling my phone. It played the media on the SD card perfectly, without interruption. I can also tell you that my MIDI controllers don't have any issue when they're connected to a laptop.

Anyway, this is the USB-C hub I'm using. Is there a different kind that would be more suited to this, or is there maybe a different issue?