Multiplayer collaboration software for iPad

As the title, recently with my girlfriend off, find a new fun. I use the ipad's built-in Boundless Note software to play collaboration and write and chat in real time, but this software is currently a big problem. First of all, when you write too much, the entire app will become stuck, and exporting the canvas pdf will crash, and then this is not the worst thing. Worst of all, every time I quit the software or crash, my handwriting is there, my girlfriend's notes are missing a large area and will not be automatically updated and synchronized, and there is no option to update manually. Since the first time I disappeared, every time I chatted with my girlfriend, I quit the software and reopen her notes, and when I was away, the messages she left under my abstract paintings were not displayed on my side. But when we both log in and write synchronously, the handwriting will be displayed normally, but after exiting, her notes are gone. Similar situations seem to occur on major platforms such as Xiaohongshu and Weibo. I don't know if my account is in the U.S. region and her cloud in Guizhou in the country region causes the server to be unstable. I want to ask if there is any similar software that can collaborate online. I have a fancy to the two software that seems to have no online collaboration function. One is procreat and the other is prodraft. Neither of them seem to support collaborative writing. We might as well go directly to WeChat. Seeing that goodnotes seems to support it, but it seems that it is extremely disgusting to eat phase changes with notability. In addition, there is no actual experiment on whether it is synchronized in real time. Not to mention this collaboration function, Boundless Record is the best. I can't stand the smell of curry Are there any recommended apps, or there are actually any software such as procreat above, but I can point out anything I haven't found. You can also charge, as long as the server is stable, it is acceptable within 100.