Jenkins pipeline not creating workspace folders when other pipelines are - jenkins

Question

I am creating a new Pipeline on an existing, functioning Jenkins server.
At the moment it is a simple multibranch pipeline with the Jenkinsfile, and a deploy.yml
The issue is that the workspace folder is not being generated.
When I do ls /var/lib/jenkins/workspace I get a list of all the other deploy jobs that have created workspaces, and a workspace.txt file where I can see the names of the workspaces that SHOULD have been created, but there is no folder for that workspace.
If I do mkdir /var/lib/jenkins/workspace/expectedname and touch /var/lib/jenkins/workspace/expectedname/deploy.yml and run it, it creates a workspace called /var/lib/jenkins/workspace/expectedname#tmp which is empty, and puts the retreived files in the one i created. If I delete the #tmp folder, it works. but it breaks again without advance notice, and it isn't feasible to keep having to create the fodler manually.
Jenkinsfile
#!groovy
node {
currentBuild.displayName = "${env.BRANCH_NAME}-${env.BUILD_NUMBER}"
config = readYaml file: "${WORKSPACE}/deploy.yml"
}
pipeline {
agent any
stages {
stage ('Fiddling'){
steps {
echo "***************** TAG: ${config.scm.tag} *****************"
}
}
}
}
deploy.yml
env:
wwwroot: "/var/www/siteroot"
type: "test"
ssh:
servername: "mysecretserver.url"
username: "jenkins"
conf:
siteTitle: "Site Title"
siteFQDN: "site.subdomain.domain.tld"
defaultFromEmail: "test#domain.tld"
sessionname: "SessionName"
mysql:
host: "localhost"
database: "mycooldb"
username: "dbuser"
password: "s3cret"
scm:
tag: "v.1.2"
jenkins log
15:28:41 Started by user JoSSte
15:28:41 > git rev-parse --is-inside-work-tree # timeout=10
15:28:41 Setting origin to git#bitbucket.org:t******/****.git
15:28:41 > git config remote.origin.url git#bitbucket.org:t******/****.git # timeout=10
15:28:41 Fetching origin...
15:28:41 Fetching upstream changes from origin
15:28:41 > git --version # timeout=10
15:28:41 > git --version # 'git version 2.17.1'
15:28:41 > git config --get remote.origin.url # timeout=10
15:28:41 using GIT_SSH to set credentials YYYYYY
15:28:41 > git fetch --tags --progress -- origin +refs/heads/*:refs/remotes/origin/* # timeout=10
15:28:42 Seen branch in repository origin/master
15:28:42 Seen branch in repository origin/noscm
15:28:42 Seen branch in repository origin/stable
15:28:42 Seen branch in repository origin/working
15:28:42 Seen 4 remote branches
15:28:44 Obtained Jenkinsfile from 5374b39f33bf6ye904134e845d60fae76a97bb09
15:28:44 Running in Durability level: MAX_SURVIVABILITY
15:28:44 [Pipeline] Start of Pipeline
15:28:44 [Pipeline] node
15:28:44 Running on Jenkins in /var/lib/jenkins/workspace/tc-d-tr_noscm
15:28:44 [Pipeline] {
15:28:44 [Pipeline] readYaml
15:28:44 [Pipeline] }
15:28:44 [Pipeline] // node
15:28:44 [Pipeline] End of Pipeline
15:28:44 java.io.FileNotFoundException: /var/lib/jenkins/workspace/tc-d-tr_noscm/deploy.yml does not exist.
15:28:44 at org.jenkinsci.plugins.pipeline.utility.steps.conf.ReadYamlStep$Execution.doRun(ReadYamlStep.java:113)
15:28:44 at org.jenkinsci.plugins.pipeline.utility.steps.AbstractFileOrTextStepExecution.run(AbstractFileOrTextStepExecution.java:32)
15:28:44 at org.jenkinsci.plugins.workflow.steps.SynchronousNonBlockingStepExecution.lambda$start$0(SynchronousNonBlockingStepExecution.java:47)
15:28:44 at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
15:28:44 at java.util.concurrent.FutureTask.run(FutureTask.java:266)
15:28:44 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
15:28:44 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
15:28:44 at java.lang.Thread.run(Thread.java:748)
15:28:44 Finished: FAILURE
Why is this job failing when all the others are not? - the only thing I can see different is that the other jobs I have don't use readYaml
Update
I made a new repo, with basically the same structure, without readYaml, on the same jenkins server - this hasn't failed in the same way - I will try to ad that to it, and see if it breaks...