containers in the same network unable to communicate - docker

Question

I have a Docker bridge network, to which are attached 2 containers:
a Node.js server running on the port 3333
a Flask server running on the port 5000
The network has this configuration:
[
{
"Name": "mynetwork",
"Id": "f94f76533b065d39515b65d20b8645c22617be51ec9335fcfad8ce707ca48841",
"Created": "2019-02-20T17:17:29.029434324+01:00",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": {},
"Config": [
{
"Subnet": "10.1.0.0/16",
"Gateway": "10.1.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"Containers": {
"c8084141e36c756710cbfa020f664127f234e407986362331ab127d415c9b074": {
"Name": "nodeContainer",
"EndpointID": "e25f8797c1b7488d7c3810d8f38c4b3dea6b9f19f17558a164b710015fdd9e1a",
"MacAddress": "02:42:0a:01:00:03",
"IPv4Address": "10.1.0.3/16",
"IPv6Address": ""
},
"f9c582d031515f4bba910286118df806a6a2b04a36917234eca09fdf335d4457": {
"Name": "flaskContainer",
"EndpointID": "fbf053f97acc7b9491c536966b640862d366d1599fbfb400915cd8bc26b04f6a",
"MacAddress": "02:42:0a:01:00:02",
"IPv4Address": "10.1.0.2/16",
"IPv6Address": ""
}
},
"Options": {},
"Labels": {}
}
]
Normally, those 2 containers communicate (nodeContainer makes requests to http://flaskContainer:5000), but this stopped to work after setting a different Subnet and Gateway (for external network constraints).
In particular, I get an error like ETIMEDOUT 10.1.0.2:3333. This makes me think that the address is correctly resolved, but for some reason, there is no answer (and in fact flaskContainer logs nothing).
As additional information:
docker exec flaskContainer curl flaskContainer
docker exec nodeContainer curl nodeContainer
obviously does not work (Failed to connect to flaskContainer port 80).
docker exec flaskContainer curl flaskContainer:5000
docker exec nodeContainer curl nodeContainer:3333
correctly give results.
docker exec flaskContainer curl nodeContainer:3333
docker exec nodeContainer curl flaskContainer:5000
goes in timeout.
Have you any idea of what can be the reason? How can I solve this?
Thank you