Please see the following:
Error Code: -2147220970
Error Message: Message size exceeded when sending context to Sandbox. Message size: ### Mb
This error occurs when a message payload is greater than 116.85 MB, and a plug-in is registered for the message. The error message includes the size of the payload that caused this error.
The limit helps ensure that users running applications can't interfere with each other based on resource constraints. The limit helps provide a level of protection from unusually large message payloads that threaten the availability and performance characteristics of the Dataverse platform.
116.85 MB is large enough that it should be rare to encounter this case. The most likely situation where this case might occur is when you retrieve a record with multiple related records that include large binary files.
If you receive this error, you can:
- Remove the plug-in for the message. If there are no plug-ins registered for the message, the operation completes without an error.
- If the error is occurring in a custom client, you can modify your code so that it doesn't attempt to perform the work in a single operation. Instead, write code to retrieve the data in smaller parts. Cited from https://learn.microsoft.com/en-us/troubleshoot/power-platform/power-apps/dataverse/dataverse-plug-ins-errors
In other terms, you cannot upload more than 116.85 MB. My suggestion is to do it in chunks if you want to go down this path.
If this is helpful please accept answer.