tremble1256 The only thing that stops the crash is disabling memory tagging, but even when I have memory tagging enabled with error notifications I don't get any notifications during the crash.
It sounds like GrapheneOS' implementation of memory tagging is catching memory corruption bug(s). It doesn't always show a crash notification when it does. I'm not sure why; someone with the technical knowledge might be able to answer that. But as an example, this kind of behaviour occurred with previous versions of Mullvad VPN when being run with GrapheneOS' MTE usage, and stopped occurring in a future version which correlated with Mullvad making safety-related changes in the code.
GrapheneOS' MTE usage is hardened compared to stock PixelOS' usage of MTE. You could test running the app with the latter, which you do by leaving memory tagging enabled for the app but disabling hardened memory allocator for it. But I suspect that Pixel OS' usage of MTE will not catch these bugs.
GrapheneOS users can use the same implementation of MTE available via ADB in the stock OS by disabling the hardened allocator with MTE enabled for the app, which will use their implementation of it as part of the standard allocator instead.