Upload issues to apps are often caused by exceeding one of the following limits:
The host instances running App Platform containers do not provide persistent data storage. Data in the host instance’s local filesystem is permanently lost after deployments and other container replacements. The local filesystem is additionally limited to 2GiB, and if it is filled to capacity, the container is detected as unhealthy and replaced.
File uploads to apps timeout after 100 seconds.
If you are exceeding one of these limits, you may need to decrease the size of your files or consider another storage option for your app.