Function Proxies forwarding to the same function app will fail if the request is to an http trigger function with routes and the route has '/' in it.

[safihamid]

Sample proxy:
"catchAllRoutes": {
"matchCondition": {
"route": "/proxy/{*path}"
},
"backendUri": "http://localhost/{path}",
"requestOverrides": {
"backend.request.headers.accept": "text/plain"
}
},

sample http trigger function:

{
"bindings": [
{
"authLevel": "anonymous",
"name": "req",
"type": "httpTrigger",
"direction": "in",
"route": "myroute/mysubroute"
},
{
"name": "$return",
"type": "http",
"direction": "out"
}
],
"disabled": false
}

[safihamid]

The fix is released.