Convert file to base64 date and assgin to a String, the string length is too long to write out. uipath is crashed


I have a problem with uipath.
I need to use HTTP, POST JSON activies to send requests to HTTP API to get the HTTP API response.
In my request, I need to convert a file(like image file) to base64 data , which the data is very large and may exceed 100,000 bytes.
When I assign this base64 data to a string variable, I cannot output this string again.
After running, the uipath broke and crashed. The information was shown as follow:
XXX has thrown an exception.
Message: Job XXXX stopped due to unexpected process termination!
The Exception Type: the Exception
System.Exception: Job XXX stopped due to unexpected process termination!
I hope somebody could help me in any way to solve the bug , thanks so much!