Can't restart docker container running subversion on my Synology NAS

[Stochastically]

I followed the instructions in this Synology knowledge base article https://kb.synology.com/en-my/DSM/tutorial/How_to_launch_an_SVN_server_based_on_Docker_on_your_Synology_NAS to setup Subversion running in a docker container on my Synology NAS. There are two components, namely the docker image marvambass/subversion and iF.SVNAdmin. It seemed to work but if the docker container is stopped and restarted, for example when the NAS is rebooted, the docker container can't be restarted. The following error message appears in the log:

httpd (pid 14) already running

My best guess is that the problem relates iF.SVNAdmin because if marvambass/subversion is used on its own, it is possible to start and stop the corresponding docker container. I posted this problem to the Synology community forum but so far there has been no response. I also contacted Synology support, but their response was to report the problem to iF.SVNAdmin. Can anyone help? Thanks, Paul