Rush mobile app keeps crashing on export

I am trying to export a 104mb file at 1080p on Rush on my iPhone 13 Pro. Plenty of memory on the device so that isn't an issue but it just keeps crashing. Just goes back to the Home Screen with no error message or explanation. It also does this just randomly, very often, while using the app. Can't believe how buggy this is for a major app from such a huge company. I'm happy with the functions of the app but they are pointless and useless if you can't export video! I've seen similar forum posts from more than three years ago - it astounds me it hasn't yet been fixed. Is there any way around this? I have tried making small changes to the duration of the video etc with no luck. We are travelling so I can't use a desktop version - but that's exactly why I am using Rush...I thought the whole point was for it to be a quick version of premiere for when you are on the go. Any advice for a fix would be appreciated!