This is most likely related to httpRuntime web.config element:
<httpRuntime
maxRequestLength= "4096" />
maxRequestLength is in integer value that specifies the limit for the input stream in KB. The default is 4096 (4 MB) set to this level with the intention to avoid users posting large files to the server.
Additionally you may need to add the executionTimeout="999999" attribute to this element.
Please note that Microsoft documentation indicates about debugging mode regarding the executionTimeout:
executionTimeout The default is "00:01:50" (110 seconds).
This time-out applies only if the debug attribute in the compilation element is False. To help to prevent shutting down the application while you are debugging, do not set this time-out to a large value.