There isn’t much that we can do here. Maybe your vault contains many large markdown files, or maybe it’s just too much for the app to handle on a phone. In either case, since there hasn’t been widespread performance issues, I don’t know what can be improved.
Again, I’d suggest syncing only a subset of your vault to use on mobile.
If you do find out that any specific file is tripping up this issue, do let us know and we can take a look.