Jenkins Docker pipeline stuck on "Waiting for next available executor" - jenkins

Question

In my project I have a Jenkins pipeline, which should execute two stages on a provided Docker image, and a third stage on the same machine but outside the container. Running this third stage on the same machine is crucial, because the previous stages produces some output that is needed later. These files are stored on the machine trough mounted volumes.
In order to be sure these files are accessible in the third stage, I manually select a specific node. Here is my pipeline (modified a little, because it's from work):
pipeline {
agent {
docker {
label 'jenkins-worker-1'
image 'custom-image:1.0'
registryUrl 'https://example.com/registry'
args '-v $HOME/.m2:/root/.m2'
}
}
stages {
stage('Test') {
steps {
sh 'mvn test'
}
}
stage('Package') {
steps {
sh 'mvn package'
sh 'mv target workdir/'
}
}
stage('Upload') {
agent {
node {
label 'jenkins-worker-1'
}
}
steps {
sh 'uploader.sh workdir'
}
}
}
}
The node is preconfigured for uploading, so I can't simply upload built target from Docker container, it has to be done from the physical machine.
And here goes my problem: while the first two stages works perfectly fine, the third stage cannot start, because: "Waiting for next available executor" suddenly appears in logs. It's obvious the node is waiting for itself, I cannot use another machine. It looks like Docker is blocking something and Jenkins thinks the node is busy, so it waits eternally.
I look for a solution, that will allow me to run stages both in and outside the container, on the same machine.
Apparently the nested stages feature would solve this problem, but unfortunately it's available since version 1.3 of pipeline plugin, but my node has 1.2.9.